With the aim of understanding the relationships between organic small molecule field-effect transistors （FETs） and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and c...With the aim of understanding the relationships between organic small molecule field-effect transistors （FETs） and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and charge carrier mobility in pentacene and regioregular poly （3-hexylthiophene） （RR-P3HT） field-effect transistors. On the basis of the results of surface morphologies and electrical properties, we presume that the charge carrier mobility is largely related to the morphology of the organic active layer. We observe that the change trends of the surface morphologies （average size and average roughness） of pentacene and RR-P3HT thin films are mutually opposite, as the thickness of the organic layer increases. Further, we demonstrate that the change trends of the field-effect mobilities of pentacene and RR-P3HT FETs are also opposite to each other, as the thickness of the organic layer increases within its limit.展开更多
In order to enhance the performance of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）, RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and anneali...In order to enhance the performance of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）, RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and annealing. This paper reports that the crystal structure, the molecule interconnection, the surface morphology, and the charge carrier mobility of RR-P3HT films are affected by vacuum relaxation and annealing. The results reveal that the field-effect mobility of RR-P3HT FETs can reach 4.17×10^-2m^2/（V·s） by vacuum relaxation at room temperature due to an enhanced local self-organization. Furthermore, it reports that an appropriate annealing temperature can facilitate the crystal structure, the orientation and the interconnection of polymer molecules. These results show that the field-effect mobility of device annealed at 150 ℃ for 10 minutes in vacuum at atmosphere and followed by placement for 20 hours in vacuum at room temperature is enhanced dramatically to 9.00×10^-2m^2/（V·s）.展开更多
High performance pentacene organic thin film transistors （OTFT） were designed and fabricated using SiO2 deposited by electron beam evaporation as gate dielectric material. Pentacene thin films were prepared on glass...High performance pentacene organic thin film transistors （OTFT） were designed and fabricated using SiO2 deposited by electron beam evaporation as gate dielectric material. Pentacene thin films were prepared on glass substrate with S-D electrode pattern made from ITO by means of thermal evaporation through self-organized process. The threshold voltage VTH was -2.75±0.1V in 0-50V range, and that subthreshold slopes were 0.42±0.05V/dec. The field-effect mobility （μEF） of OTFT device increased with the increase of VDS, but the μEF of OTFT device increased and then decreased with increased VGS when VDS was kept constant. When VDS was -50V, on/off current ratio was 0.48×10^5 and subthreshold slope was 0.44V/dec. The μEF was 1.10cm^2/（V.s）, threshold voltage was -2.71V for the OTFT device.展开更多
This paper investigates the effects of concentration on the crystalline structure, the morphology, and the charge carrier mobility of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）...This paper investigates the effects of concentration on the crystalline structure, the morphology, and the charge carrier mobility of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）. The RR-P3HT FETs with RR-P3HT as an active layer with different concentrations of RR-P3HT solution from 0.5 wt% to 2 wt% are prepared. The results indicate that the performance of RR-P3HT FETs improves drastically with the increase of RR-P3HT weight percentages in chloroform solution due to the formation of more microcrystalline lamellae and bigger nanoscale islands. It finds that the field-effect mobility of RR-P3HT FET with 2 wt% can reach 5.78×10^-3 cm^2/Vs which is higher by a factor of 13 than that with 0.5 wt%. Further, an appropriate thermal annealing is adopted to improve the performance of RR-P3HT FETs. The field-effect mobility of RR-P3HT FETs increases drastically to 0.09 cm^2/Vs by thermal annealing at 150 ℃, and the value of on/off current ratio can reach 104.展开更多
Inorganic lead halide perovskite nanocrystals(NCs)with superior photoelectric properties are expected to have excellent performance in many fields.However,the anion exchange changes their features and is unfavorable f...Inorganic lead halide perovskite nanocrystals(NCs)with superior photoelectric properties are expected to have excellent performance in many fields.However,the anion exchange changes their features and is unfavorable for their applications in many fields.Hence,impeding anion exchange is important for improving the composition stability of inorganic lead halide perovskite NCs.Herein,CsPb X3(X=Cl,Br)NCs are coated with Cs4PbX6 shell to impede anion exchange and reduce anion mobility.The Cs4PbX6 shell is facily fabricated on CsPbX3 NCs through high temperature injection method.Anion exchange experiments demonstrate that the Cs4 PbX6 shell completely encapsulates CsPbX3 NCs and greatly improves the composition stability of CsPbX3 NCs.Moreover,our work also sheds light on the potential design approaches of various heterostructures to expand the application of CsPbM3(M=Cl,Br,I)NCs.展开更多
In this paper, the electroluminescence quenching mechanism in a 5,6,11,12-tetraphenylnaphthacene （Rubrene） doped host-guest system is studied by utilizing a specially designed organic light-emitting diode with an em...In this paper, the electroluminescence quenching mechanism in a 5,6,11,12-tetraphenylnaphthacene （Rubrene） doped host-guest system is studied by utilizing a specially designed organic light-emitting diode with an emission layer consisting of a few periodic host/guest structures. Tris-（8-hydroxyquinoline） aluminium （Alq3） and Rubrene are used as the host and the guest, respectively. The thickness variation of the guest layer in each period enables the study of the effect of molecule aggregation, and the thickness variation of the host layer suggests a long range quenching mechanism of dipole-dipole interaction. The long range quenching mechanism is a Forster process, and the FSrster radius of Rubrene is between 3 and 10 nm.展开更多
The properties of top-contact organic thin-film transistors （TC-OTFTs） using ultra-thin 2, 9-dimethyl-4, 7- diphenyl-1, 10-phenanthroline （BCP） as a hole-blocking interlayer have been improved significantly and a ...The properties of top-contact organic thin-film transistors （TC-OTFTs） using ultra-thin 2, 9-dimethyl-4, 7- diphenyl-1, 10-phenanthroline （BCP） as a hole-blocking interlayer have been improved significantly and a BCP interlayer was inserted into the middle of the pentacene active layer. This paper obtains a fire-new transport mode of an OTFT device with double-conductible channels. The accumulation and transfer of the hole carriers arc limited by the BCP interlayer in the vertical region of the channel. A huge amount of carriers is located not only at the interface between pentacene and the gate insulator, but also at the two interfaces of pentacene/BCP interlayer and pentacene/gate insulator, respectively. The results suggest that the BCP interlayer may be useful to adjust the hole accumulation and transfer, and can increase the hole mobility and output current of OTFTs. The TC-OTFTs with a BCP interlayer at VDS = --20 V showed excellent hole mobility μFE and threshold voltage VTH of 0.58 cm^2/（V-s） and -4.6 V, respectively.展开更多
We investigate the effects of （N,N’-diphenyl）-N,N’-bis（1-naphthyl）-1,1’-biphenyl-4,4’-diamine （NPB） buffer layers on charge collection in inverted ZnO/MEH-PPV hybrid devices. The insertion of a 3-nm NPB thin...We investigate the effects of （N,N’-diphenyl）-N,N’-bis（1-naphthyl）-1,1’-biphenyl-4,4’-diamine （NPB） buffer layers on charge collection in inverted ZnO/MEH-PPV hybrid devices. The insertion of a 3-nm NPB thin layer enhances the efficiency of charge collection by improving charge transport and reducing the interface energy barrier, resulting in better device performances. S-shaped light J–V curve appears when the thickness of the NPB layer reaches 25 nm, which is induced by the inefficient charge extraction from MEH-PPV to Ag. Capacitance–voltage measurements are performed to further investigate the influence of the NPB layer on charge collection from both simulations and experiments.展开更多
The luminescence processes of metal complexes are complicated by intramolecular charge (energy) transfer from the metal to the ligand or from the ligand to the metal. The charge transfer strongly influences the excite...The luminescence processes of metal complexes are complicated by intramolecular charge (energy) transfer from the metal to the ligand or from the ligand to the metal. The charge transfer strongly influences the excited state of the ligand and its luminescence characteristics. The luminescence characteristics of tris(8-hydroxyquinoline) aluminum (Alq3) and tris(8-hydroxyquinoline) gallium (Gaq3) are investigated to reveal the effect of the metal ion on the ligand. Emission from the complexes shows a significant red shift as the size of the metal ion increases from Al to Ga because of more efficient charge transfer from the metal to the ligand. Theoretical calculations on the structure and transition characteristics of the excited states of Alq3 and Gaq3 were performed. The calculated emission wavelength agrees with the experimental value and the effect of the metal electron cloud on the emission wavelength is clarified.展开更多
Ce3+/Dy3+/Tb3+/Eu3+/Mn2+and Cr3+ions co-doped Zn3 Al2 Ge2 O10 phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn3 Al2 Ge2 O10 phosp...Ce3+/Dy3+/Tb3+/Eu3+/Mn2+and Cr3+ions co-doped Zn3 Al2 Ge2 O10 phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn3 Al2 Ge2 O10 phosphor,Emission,excitation spectra and decay curves confirm the tunable luminescence.Different degrees of the decrease of emission FWHM in Zn3 Al2 Ge2 O10:0.02 Cr3+,RE(RE=Ce3+,Dy3+,Tb3+,Eu3+)and Zn3 Al2 Ge2 O10:0.02 Cr3+,Mn2+are observed.The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect,and the nephelauxetic effect is dominant.Therefore,the emission FWHM decreases with the increasing concentration of Mn2+/Tb3+/Eu3+in Zn3 Al2 Ge2 O10:0.02 Cr3+,and for Zn3 Al2 Ge2 O10:0.02 Cr3+,Ce3+and Zn3 Al2 Ge2 O10:0.02 Cr3+,Dy3+,it is a constant.The variation of Zn3 Al2 Ge2 O10:0.02 Cr3+,Tb3+is more obvious than that of Zn3 Al2 Ge2 O10:0.02 Cr3+,Eu3+,because Tb3+ion has smaller electronegativity.Thus,the tunable luminescence of Cr3+can be realized by co-doping different ions.And these phosphors have potential applications in light-emitting diodes for plant growth.展开更多
Bulk heterojunction organic solar cells (OSCs) based on the blend of poly(2-methoxy-5(2′-ethyl-hexyloxy)-1,4-phenylenevinylene (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with different weight rat...Bulk heterojunction organic solar cells (OSCs) based on the blend of poly(2-methoxy-5(2′-ethyl-hexyloxy)-1,4-phenylenevinylene (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with different weight ratios (from 1:3 to 1:5) have been fabricated and the effect of annealing treatment on the performance of OSCs has also been studied. Experimental results point to the best optimized doping concentration 1:4 for MEH-PPV:PCBM. Furthermore, it is found that the devices with annealing treatment at 150°C with 8 min show better performance compared with the devices without treatment. The series resistance (R s) is decreased, while the shunt resistance (R sh) increased by nearly 1.5 times. The short-circuit current density (J sc) and fill factor (FF) are improved by annealing treatment. As a result, the power conversion efficiency (PCE) of the devices increases from 0.49 % to 1.21 % with the ratio of 1:3 and from 1.09% to 1.42% with the ratio of 1:4.展开更多
The enhanced performance of a squaraine compound, with 2,4-bis[4-（N,N-diisobutylamino）-2,6-dihydroxyphenyl] squaraine as the donor and [6,6]-phenyl-C71-butyric acid methyl ester （PC71BM） as the acceptor, in soluti...The enhanced performance of a squaraine compound, with 2,4-bis[4-（N,N-diisobutylamino）-2,6-dihydroxyphenyl] squaraine as the donor and [6,6]-phenyl-C71-butyric acid methyl ester （PC71BM） as the acceptor, in solution-processed or- ganic photovoltaic devices is obtained by using UV-ozone-treated MoO3 as the hole-collecting buffer layer. The optimized thickness of the MoO3 layer is 8 nm, at which the device shows the best power conversion efficiency （PCE） among all devices, resulting from a balance of optical absorption and charge transport. After being treated by UV-ozone for 10 min, the transmittance of the MoO3 film is almost unchanged. Atomic force microscopy results show that the treated surface morphology is improved. A high PCE of 3.99% under AM 1.5 G illumination （100 mW/cm2） is obtained.展开更多
The contact effect on the performances of organic thin film transistors is studied here. A C60 ultrathin layer is inserted between Al source-drain electrode and pentacene to reduce the contact resistance. By a 3 nm C6...The contact effect on the performances of organic thin film transistors is studied here. A C60 ultrathin layer is inserted between Al source-drain electrode and pentacene to reduce the contact resistance. By a 3 nm C60 modification, the injection barrier is lowered and the contact resistance is reduced. Thus, the field-effect mobility increases from 0.12 to 0.52 cm2/（V.s）. It means that inserting a C60 ultra thin layer is a good method to improve the organic thin film transistor （OTFT） performance. The output curve is simulated by using a charge drift model. Considering the contact effect, the field effect mobility is improved to 1.15 cm2/（V-s）. It indicates that further reducing the contact resistance of OTFTs should be carried out.展开更多
The properties of poly（3-hexylthiophene）：（6,6）-phenyl C61 butyric acid methyl ester （P3HT：PCBM） organic pho- tovoltaic devices （OPVs） with an indium tin oxide （ITO） anode treated by a KMnO4 solution are in...The properties of poly（3-hexylthiophene）：（6,6）-phenyl C61 butyric acid methyl ester （P3HT：PCBM） organic pho- tovoltaic devices （OPVs） with an indium tin oxide （ITO） anode treated by a KMnO4 solution are investigated. The optimized KMnO4 solution has a concentration of 50 rag/L, and ITO is treated for 15 min. The modification of ITO anode results in an enhancement of the power conversion efficiency （PCE） of the device, which is responsible for the increase of the photocurrent. The performance enhancement is attributed to the work function modification of the ITO substrate through the strong oxygenation of KMnO4, and then the charge collection efficiency is improved.展开更多
A series of polymer solar cells(PSCs) based on poly(diketopyrrolopyrrole-terthiophene)(PDPP3T) and[6,6]-phenyl-C71-butyric acid methyl ester(PC71BM) as active layer were fabricated to investigate the effect of 1,8-dii...A series of polymer solar cells(PSCs) based on poly(diketopyrrolopyrrole-terthiophene)(PDPP3T) and[6,6]-phenyl-C71-butyric acid methyl ester(PC71BM) as active layer were fabricated to investigate the effect of 1,8-diiodooctane(DIO) on the performance of PSCs. The power conversion efficiency(PCE) of PSCs was increased from 3.77 % to 4.37 % for the cells with DIO additive. The underlying reason may be attributed to that DIO additive could make PC71 BM more dispersive in the active layer,forming a better bi-continuous interpenetrating network for excition dissociation and charge carrier transport. Therefore, the short circuit current density(JSC) and fill factor(FF) was increased from 8.25 to 9.18 mA/cm2and from67.2 % to 70.0 % for the PSCs with DIO additive compared with PSCs without DIO additive.展开更多
We fabricate inverted organic/inorganic hybrid solar cells based on vertically oriented ZnO nanorods and polymer MEH-PPV. The morphology of ZnO nanorods and ZnO nanorods/MEH-PPV hybrid structure is depicted by using s...We fabricate inverted organic/inorganic hybrid solar cells based on vertically oriented ZnO nanorods and polymer MEH-PPV. The morphology of ZnO nanorods and ZnO nanorods/MEH-PPV hybrid structure is depicted by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscope (AFM), respectively. It is observed that ZnO nanorods array grows primarily aligned along the perpendicular direction of the ITO substrate. The MEH-PPV molecule does not enter the interspace between ZnO nanorods completely according to SEM picture. It results in the small and bad contact area between ZnO nanorods and MEH-PPV. To improve the photovoltaic performance, we also fabricate another kind of photovoltaic (PV) device modified by N719 dye, and exploit the effect of N719. After the modification of ZnO nanorods by N719, not only Jsc increases from 0.257 mA/cm2 to 0.42 mA/cm2, but also Voc enhances from 0.37 V to 0.42 V. Insert LiF buffer layer between MEH-PPV and anode, Jsc of 1.05 mA/cm2 is obtained, and it is 2.5 times that the device without LiF.展开更多
Controlling the morphology of the MAPbI3-xClx active layer has remained a challenge towards advancing perovskite solar cells （PvSCs）. Here, we demonstrate that a low temperature additive dripping （AD） treatment st...Controlling the morphology of the MAPbI3-xClx active layer has remained a challenge towards advancing perovskite solar cells （PvSCs）. Here, we demonstrate that a low temperature additive dripping （AD） treatment step, using diphenyl ether （DPE）, can significantly improve the power conversion efficiency （PCE）, compared to the control device using chlorobenzene （CB）, by 15% up to 16.64%, with a high current density （Jsc） of 22.67 mA/cm^2. We chose DPE for its small and appropriate dipole moment to adjust the solubility of the MAPbI3-xClx precursor during the formation of the intermediate phase and the MAPbI3-xClx phase. The low DPE vapor pressure provides a longer processing window for the removal of residual dimethylformamide （DMF）, during the annealing process, for improved perovskite formation. Imaging and X-ray analysis both reveal that the MAPbI3-xClx film exhibits enlarged grains with increased crystallinity. Together, these improvements result in reduced carrier recombination and hole trap-state density in the MAPbI3-xClx film, while minimizing the hysteresis problem typical of PvSCs. These results show that the AD approach is a promising technique for improving PvSCs.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10774013 and 10804006)the National High Technology Research and Development Program of China (Grant No. 2006AA03Z412)+3 种基金the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070004024)the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education, China (Grant No. 20070004031)the New Star Plan of Science and Technology of Beijing, China(Grant No. 2007A024)the research grants from the Academy of Sciences for the Developing World (Grant No. B08002)
文摘With the aim of understanding the relationships between organic small molecule field-effect transistors （FETs） and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and charge carrier mobility in pentacene and regioregular poly （3-hexylthiophene） （RR-P3HT） field-effect transistors. On the basis of the results of surface morphologies and electrical properties, we presume that the charge carrier mobility is largely related to the morphology of the organic active layer. We observe that the change trends of the surface morphologies （average size and average roughness） of pentacene and RR-P3HT thin films are mutually opposite, as the thickness of the organic layer increases. Further, we demonstrate that the change trends of the field-effect mobilities of pentacene and RR-P3HT FETs are also opposite to each other, as the thickness of the organic layer increases within its limit.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10774013 and 10804006)the National High Technology Research and Development Program of China (Grant No 2006AA03Z0412)+4 种基金the Research Fund for the Doctoral Program of Higher Education of China (Grant No 20070004024)the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education (Grant No 20070004031)the Beijing NOVA program (Grant No 2007A024)the the 111 of China (Grant No B08002)the research grants from the Academy of Sciences for the Developing World
文摘In order to enhance the performance of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）, RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and annealing. This paper reports that the crystal structure, the molecule interconnection, the surface morphology, and the charge carrier mobility of RR-P3HT films are affected by vacuum relaxation and annealing. The results reveal that the field-effect mobility of RR-P3HT FETs can reach 4.17×10^-2m^2/（V·s） by vacuum relaxation at room temperature due to an enhanced local self-organization. Furthermore, it reports that an appropriate annealing temperature can facilitate the crystal structure, the orientation and the interconnection of polymer molecules. These results show that the field-effect mobility of device annealed at 150 ℃ for 10 minutes in vacuum at atmosphere and followed by placement for 20 hours in vacuum at room temperature is enhanced dramatically to 9.00×10^-2m^2/（V·s）.
基金supported by the National Natural Science Foundation of China (Grant No 60576016)the National High Technology Research and Development Program of China (Grant No 2006AA03Z0412)+3 种基金the Beijing Natural Science Foundation of China (Grant No 2073030)the National Grand Fundamental Research 973 Program of China (Grant No 2003CB314707)the National Natural Science Foundation of China (Grant No 10434030)the Excellent Doctor's Science and Technology Innovation Foundation of Beijing Jiaotong University of China (Grant No 48024)
文摘High performance pentacene organic thin film transistors （OTFT） were designed and fabricated using SiO2 deposited by electron beam evaporation as gate dielectric material. Pentacene thin films were prepared on glass substrate with S-D electrode pattern made from ITO by means of thermal evaporation through self-organized process. The threshold voltage VTH was -2.75±0.1V in 0-50V range, and that subthreshold slopes were 0.42±0.05V/dec. The field-effect mobility （μEF） of OTFT device increased with the increase of VDS, but the μEF of OTFT device increased and then decreased with increased VGS when VDS was kept constant. When VDS was -50V, on/off current ratio was 0.48×10^5 and subthreshold slope was 0.44V/dec. The μEF was 1.10cm^2/（V.s）, threshold voltage was -2.71V for the OTFT device.
基金supported by the National Natural Science Foundation of China (Grant Nos 10774013,10804006)the National High Technology Research and Development Program of China (Grant No 2006AA03Z0412)+3 种基金the Research Fund for the Doctoral Program of Higher Education of China (Grant No 20070004024)The Research Fund for the Youth Scholars of the Doctoral Program of Higher Education (Grant No 20070004031)the Beijing NOVA Program (Grant No 2007A024)the 111 Project(Grant No B08002)
文摘This paper investigates the effects of concentration on the crystalline structure, the morphology, and the charge carrier mobility of regioregular poly（3-hexylthiophene） （RR-P3HT） field-effect transistors （FETs）. The RR-P3HT FETs with RR-P3HT as an active layer with different concentrations of RR-P3HT solution from 0.5 wt% to 2 wt% are prepared. The results indicate that the performance of RR-P3HT FETs improves drastically with the increase of RR-P3HT weight percentages in chloroform solution due to the formation of more microcrystalline lamellae and bigger nanoscale islands. It finds that the field-effect mobility of RR-P3HT FET with 2 wt% can reach 5.78×10^-3 cm^2/Vs which is higher by a factor of 13 than that with 0.5 wt%. Further, an appropriate thermal annealing is adopted to improve the performance of RR-P3HT FETs. The field-effect mobility of RR-P3HT FETs increases drastically to 0.09 cm^2/Vs by thermal annealing at 150 ℃, and the value of on/off current ratio can reach 104.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474018,61704007,and 61575019)the National Key Research and Development Program of China(Grant No.2017YFB0404501)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.2017RC034)the Shenzhen China Star Optoelectronics Technology Co.,Ltd
文摘Inorganic lead halide perovskite nanocrystals(NCs)with superior photoelectric properties are expected to have excellent performance in many fields.However,the anion exchange changes their features and is unfavorable for their applications in many fields.Hence,impeding anion exchange is important for improving the composition stability of inorganic lead halide perovskite NCs.Herein,CsPb X3(X=Cl,Br)NCs are coated with Cs4PbX6 shell to impede anion exchange and reduce anion mobility.The Cs4PbX6 shell is facily fabricated on CsPbX3 NCs through high temperature injection method.Anion exchange experiments demonstrate that the Cs4 PbX6 shell completely encapsulates CsPbX3 NCs and greatly improves the composition stability of CsPbX3 NCs.Moreover,our work also sheds light on the potential design approaches of various heterostructures to expand the application of CsPbM3(M=Cl,Br,I)NCs.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10974013,10774013,10804006 and 60825407)the Research Fund for the Doctoral Program of Higher Education,China (Grant Nos. 20070004024 and 20070004031)+2 种基金the Beijing Science and Technology New Star Program,China (Grant No. 2007A024),and the 111 Project (Grant No. B08002)the Excellent Doctor’s Science and Technology Innovation Foundation of Beijing Jiaotong University,China (Grant No. 141049522)the Research Grants from the Academy of Sciences for the Third World (TWAS)
文摘In this paper, the electroluminescence quenching mechanism in a 5,6,11,12-tetraphenylnaphthacene （Rubrene） doped host-guest system is studied by utilizing a specially designed organic light-emitting diode with an emission layer consisting of a few periodic host/guest structures. Tris-（8-hydroxyquinoline） aluminium （Alq3） and Rubrene are used as the host and the guest, respectively. The thickness variation of the guest layer in each period enables the study of the effect of molecule aggregation, and the thickness variation of the host layer suggests a long range quenching mechanism of dipole-dipole interaction. The long range quenching mechanism is a Forster process, and the FSrster radius of Rubrene is between 3 and 10 nm.
基金supported by the National High Technology Research and Development Program of China (Grant No 2006AA03Z0412)the National Natural Science Foundation of China (Grant Nos 10774013 and 10804006)+4 种基金the Excellent Doctor’s Science and Technology Innovation Foundation of Beijing Jiaotong University (Grant No 48024)the Foundation of Beijing Jiaotong University (Grant No 2005SM057)the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education (Grant No 20070004031)the Beijing NOVA program (Grant No 2007A024)Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘The properties of top-contact organic thin-film transistors （TC-OTFTs） using ultra-thin 2, 9-dimethyl-4, 7- diphenyl-1, 10-phenanthroline （BCP） as a hole-blocking interlayer have been improved significantly and a BCP interlayer was inserted into the middle of the pentacene active layer. This paper obtains a fire-new transport mode of an OTFT device with double-conductible channels. The accumulation and transfer of the hole carriers arc limited by the BCP interlayer in the vertical region of the channel. A huge amount of carriers is located not only at the interface between pentacene and the gate insulator, but also at the two interfaces of pentacene/BCP interlayer and pentacene/gate insulator, respectively. The results suggest that the BCP interlayer may be useful to adjust the hole accumulation and transfer, and can increase the hole mobility and output current of OTFTs. The TC-OTFTs with a BCP interlayer at VDS = --20 V showed excellent hole mobility μFE and threshold voltage VTH of 0.58 cm^2/（V-s） and -4.6 V, respectively.
基金Project supported by the National Basic Research Program of China(Grant No.2010CB327704)the National Natural Science Foundation of China(Grant No.51272022)+2 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NCET-10-0220)the Research Fund for the Doctoral Program of Higher Education,China(Grant No.20120009130005)the Fundamental Research Funds for the Central Universities,China(Grant No.2012JBZ001)
文摘We investigate the effects of （N,N’-diphenyl）-N,N’-bis（1-naphthyl）-1,1’-biphenyl-4,4’-diamine （NPB） buffer layers on charge collection in inverted ZnO/MEH-PPV hybrid devices. The insertion of a 3-nm NPB thin layer enhances the efficiency of charge collection by improving charge transport and reducing the interface energy barrier, resulting in better device performances. S-shaped light J–V curve appears when the thickness of the NPB layer reaches 25 nm, which is induced by the inefficient charge extraction from MEH-PPV to Ag. Capacitance–voltage measurements are performed to further investigate the influence of the NPB layer on charge collection from both simulations and experiments.
基金supported by the National Natural Science Foundation of China (10804006, 21003009, 21074055 and 10774013)the National Natural Science Fund for Distinguished Young Scholars (60825407)+6 种基金the National Basic Research Program of China (2010CB327704)the Natural Science Foundation of Beijing (1102028)111 Project (B08002)the NUST Research Funding (2010ZDJH04)Beijing Jiaotong University (2009J-BZ019-4 and 2007RC078)the State Key Laboratory of Crystal Materials,Shandong University (KF0806)Beijing National Laboratory for Molecular Sciences
文摘The luminescence processes of metal complexes are complicated by intramolecular charge (energy) transfer from the metal to the ligand or from the ligand to the metal. The charge transfer strongly influences the excited state of the ligand and its luminescence characteristics. The luminescence characteristics of tris(8-hydroxyquinoline) aluminum (Alq3) and tris(8-hydroxyquinoline) gallium (Gaq3) are investigated to reveal the effect of the metal ion on the ligand. Emission from the complexes shows a significant red shift as the size of the metal ion increases from Al to Ga because of more efficient charge transfer from the metal to the ligand. Theoretical calculations on the structure and transition characteristics of the excited states of Alq3 and Gaq3 were performed. The calculated emission wavelength agrees with the experimental value and the effect of the metal electron cloud on the emission wavelength is clarified.
基金Projects supported by the National Natural Science Foundation of China(61575019,11474018,61775013),ChinaThe authors express the thanks to the Fundamental ResearchFunds for the Central Universities under Grant No. 2018YJS166,China and the Fundamental Research Funds for the Central Universitieswith the Grant No. 2016JBM066,No. 2017RC015, No.2017JBZ105, China.
文摘Ce3+/Dy3+/Tb3+/Eu3+/Mn2+and Cr3+ions co-doped Zn3 Al2 Ge2 O10 phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn3 Al2 Ge2 O10 phosphor,Emission,excitation spectra and decay curves confirm the tunable luminescence.Different degrees of the decrease of emission FWHM in Zn3 Al2 Ge2 O10:0.02 Cr3+,RE(RE=Ce3+,Dy3+,Tb3+,Eu3+)and Zn3 Al2 Ge2 O10:0.02 Cr3+,Mn2+are observed.The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect,and the nephelauxetic effect is dominant.Therefore,the emission FWHM decreases with the increasing concentration of Mn2+/Tb3+/Eu3+in Zn3 Al2 Ge2 O10:0.02 Cr3+,and for Zn3 Al2 Ge2 O10:0.02 Cr3+,Ce3+and Zn3 Al2 Ge2 O10:0.02 Cr3+,Dy3+,it is a constant.The variation of Zn3 Al2 Ge2 O10:0.02 Cr3+,Tb3+is more obvious than that of Zn3 Al2 Ge2 O10:0.02 Cr3+,Eu3+,because Tb3+ion has smaller electronegativity.Thus,the tunable luminescence of Cr3+can be realized by co-doping different ions.And these phosphors have potential applications in light-emitting diodes for plant growth.
基金Supported by the National Natural Science Foundation of China (Grant Nos.10774013 and 10804006)the National Natural Science Funds for Distinguished Young Scholar (Grant No. 60825407)+4 种基金the Major State Basic Research Development Program of China (Grant No.2010CB327705)the Beijing Jiaotong University (Grant No.2007RC065)the Research Fund for the Doctoral Program of Higher Education (Grant No.20070004024)the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education (Grant No.20070004031)the 111 Project (Grant No.B08002)
文摘Bulk heterojunction organic solar cells (OSCs) based on the blend of poly(2-methoxy-5(2′-ethyl-hexyloxy)-1,4-phenylenevinylene (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with different weight ratios (from 1:3 to 1:5) have been fabricated and the effect of annealing treatment on the performance of OSCs has also been studied. Experimental results point to the best optimized doping concentration 1:4 for MEH-PPV:PCBM. Furthermore, it is found that the devices with annealing treatment at 150°C with 8 min show better performance compared with the devices without treatment. The series resistance (R s) is decreased, while the shunt resistance (R sh) increased by nearly 1.5 times. The short-circuit current density (J sc) and fill factor (FF) are improved by annealing treatment. As a result, the power conversion efficiency (PCE) of the devices increases from 0.49 % to 1.21 % with the ratio of 1:3 and from 1.09% to 1.42% with the ratio of 1:4.
基金Project supported by the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NCET-10-0220)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120009130005)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.2012JBZ001)
文摘The enhanced performance of a squaraine compound, with 2,4-bis[4-（N,N-diisobutylamino）-2,6-dihydroxyphenyl] squaraine as the donor and [6,6]-phenyl-C71-butyric acid methyl ester （PC71BM） as the acceptor, in solution-processed or- ganic photovoltaic devices is obtained by using UV-ozone-treated MoO3 as the hole-collecting buffer layer. The optimized thickness of the MoO3 layer is 8 nm, at which the device shows the best power conversion efficiency （PCE） among all devices, resulting from a balance of optical absorption and charge transport. After being treated by UV-ozone for 10 min, the transmittance of the MoO3 film is almost unchanged. Atomic force microscopy results show that the treated surface morphology is improved. A high PCE of 3.99% under AM 1.5 G illumination （100 mW/cm2） is obtained.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10774013,10974013,60978060 and 10804006)the Research Fund for the Doctoral Program of Higher Education,China(Grant Nos.20090009110027,20070004024 and 20070004031)+1 种基金the Beijing Municipal Science and Technology Commission(Grant No.1102028)the National Basic Research Program of China(Grant No.2010CB327704)
文摘The contact effect on the performances of organic thin film transistors is studied here. A C60 ultrathin layer is inserted between Al source-drain electrode and pentacene to reduce the contact resistance. By a 3 nm C60 modification, the injection barrier is lowered and the contact resistance is reduced. Thus, the field-effect mobility increases from 0.12 to 0.52 cm2/（V.s）. It means that inserting a C60 ultra thin layer is a good method to improve the organic thin film transistor （OTFT） performance. The output curve is simulated by using a charge drift model. Considering the contact effect, the field effect mobility is improved to 1.15 cm2/（V-s）. It indicates that further reducing the contact resistance of OTFTs should be carried out.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10974013 and 60978060)the Research Fund for the Doctoral Program of Higher Education,China(Grant No.20090009110027)+3 种基金the Beijing Municipal Natural Science Foundation,China(Grant No.1102028)the New Century Excellent Talents in University,China(Grant No.NCET-10-0220)the Fundamental Research Funds for the Central Universities,China(Grant No.2012JBZ001)the Technology Innovation Fund for Outstanding Ph.D.Students of Beijing Jiaotong University,China(Grant No.48034)
文摘The properties of poly（3-hexylthiophene）：（6,6）-phenyl C61 butyric acid methyl ester （P3HT：PCBM） organic pho- tovoltaic devices （OPVs） with an indium tin oxide （ITO） anode treated by a KMnO4 solution are investigated. The optimized KMnO4 solution has a concentration of 50 rag/L, and ITO is treated for 15 min. The modification of ITO anode results in an enhancement of the power conversion efficiency （PCE） of the device, which is responsible for the increase of the photocurrent. The performance enhancement is attributed to the work function modification of the ITO substrate through the strong oxygenation of KMnO4, and then the charge collection efficiency is improved.
基金supported by the Fundamental Research Funds for the Central Universities (2014YJS139)
文摘A series of polymer solar cells(PSCs) based on poly(diketopyrrolopyrrole-terthiophene)(PDPP3T) and[6,6]-phenyl-C71-butyric acid methyl ester(PC71BM) as active layer were fabricated to investigate the effect of 1,8-diiodooctane(DIO) on the performance of PSCs. The power conversion efficiency(PCE) of PSCs was increased from 3.77 % to 4.37 % for the cells with DIO additive. The underlying reason may be attributed to that DIO additive could make PC71 BM more dispersive in the active layer,forming a better bi-continuous interpenetrating network for excition dissociation and charge carrier transport. Therefore, the short circuit current density(JSC) and fill factor(FF) was increased from 8.25 to 9.18 mA/cm2and from67.2 % to 70.0 % for the PSCs with DIO additive compared with PSCs without DIO additive.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10774013, 10974013, and 60825407)the Research Fund for the Doctoral Program of Higher Education (Grant Nos. 20070004024 and 20070004031)+2 种基金the Beijing NOVA Program (Grant No. 2007A024)the 111 Project (Grant No. B08002)research grants from TWAS
文摘We fabricate inverted organic/inorganic hybrid solar cells based on vertically oriented ZnO nanorods and polymer MEH-PPV. The morphology of ZnO nanorods and ZnO nanorods/MEH-PPV hybrid structure is depicted by using scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscope (AFM), respectively. It is observed that ZnO nanorods array grows primarily aligned along the perpendicular direction of the ITO substrate. The MEH-PPV molecule does not enter the interspace between ZnO nanorods completely according to SEM picture. It results in the small and bad contact area between ZnO nanorods and MEH-PPV. To improve the photovoltaic performance, we also fabricate another kind of photovoltaic (PV) device modified by N719 dye, and exploit the effect of N719. After the modification of ZnO nanorods by N719, not only Jsc increases from 0.257 mA/cm2 to 0.42 mA/cm2, but also Voc enhances from 0.37 V to 0.42 V. Insert LiF buffer layer between MEH-PPV and anode, Jsc of 1.05 mA/cm2 is obtained, and it is 2.5 times that the device without LiF.
基金The authors gratefully acknowledge the Fundamental Research Funds for the Central Universities （No. S16JB00060）, the National Science Foundation, NSF- PECASE award （No. CBET-0954985） and the National Natural Science Foundation of China （No. 61575019） for partial support of this work. D. H. also thanks the support from the China Scholarship Council. The AFM SEM used were supported by the Yale Institute for Nanoscience and Quantum Engineering （YINQE） and NSF MRSEC DMR 1119826 for Center for Research on Interface Structures and Phenomena （CRISP）. The GIWAXS obtained at 1W1A, BSRF. The authors further thank scientists of Diffuse X-ray Scattering Station in the experiments for the assistance with GIWAXS measurements, as well as Dr. Yuchuan Shao from the Depai-anent of Electrical Engineering, Yale University for the useful discussion.
文摘Controlling the morphology of the MAPbI3-xClx active layer has remained a challenge towards advancing perovskite solar cells （PvSCs）. Here, we demonstrate that a low temperature additive dripping （AD） treatment step, using diphenyl ether （DPE）, can significantly improve the power conversion efficiency （PCE）, compared to the control device using chlorobenzene （CB）, by 15% up to 16.64%, with a high current density （Jsc） of 22.67 mA/cm^2. We chose DPE for its small and appropriate dipole moment to adjust the solubility of the MAPbI3-xClx precursor during the formation of the intermediate phase and the MAPbI3-xClx phase. The low DPE vapor pressure provides a longer processing window for the removal of residual dimethylformamide （DMF）, during the annealing process, for improved perovskite formation. Imaging and X-ray analysis both reveal that the MAPbI3-xClx film exhibits enlarged grains with increased crystallinity. Together, these improvements result in reduced carrier recombination and hole trap-state density in the MAPbI3-xClx film, while minimizing the hysteresis problem typical of PvSCs. These results show that the AD approach is a promising technique for improving PvSCs.
