The effect of the valence band tail width on the open circuit voltage of P3HT:PCBM bulk heterojunction solar cell is investigated by using the AMPS-1D computer program. An effective medium model with exponential vale...The effect of the valence band tail width on the open circuit voltage of P3HT:PCBM bulk heterojunction solar cell is investigated by using the AMPS-1D computer program. An effective medium model with exponential valence and conduction band tail states is used to simulate the photovoltaic cell. The simulation result shows that the open circuit voltage depends Iinearly on the logarithm of the generation rate and the slope depends on the width of the valence band tail. The open circuit voltage decreases with the increasing width of the band tail. The dark and light ideality factors increase with the width of the valence band tail.展开更多
We use the method of device simulation to study the losses and influences of geminate and bimolecular recombinations on the performances and properties of the bulk heterojunction organic solar cells. We find that a fr...We use the method of device simulation to study the losses and influences of geminate and bimolecular recombinations on the performances and properties of the bulk heterojunction organic solar cells. We find that a fraction of electrons(holes)in the device are collected by anode(cathode). The direction of the corresponding current is opposite to the direction of photocurrent. And the current density increases with the bias increasing but decreases as bimolecular recombination(BR)or geminate recombination(GR) intensity increases. The maximum power, short circuit current, and fill factor display a stronger dependence on GR than on BR. While the influences of GR and BR on open circuit voltage are about the same.Our studies shed a new light on the loss mechanism and may provide a new way of improving the efficiency of bulk heterojunction organic solar cells.展开更多
Polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are fabricated by using 1,8-diiodooctane (DIO) as a solvent additive to control the dop...Polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are fabricated by using 1,8-diiodooctane (DIO) as a solvent additive to control the doping density of the PSCs. It is shown that the processing of DIO does not change the doping density of the P3HT phase, while it causes a dramatic reduction of the doping density of the PCBM phase, which decreases the doping density of the whole blend layer from 3.7 × 10^16 cm-3 to 1.2 ×10^16 cm-3. The reduction of the doping density in the PCBM phase originates from the increasing crystallinity of PCBM with DIO addition, and it leads to a decreasing doping density in the blend film and improves the short circuit current of the PSCs.展开更多
In this work, the influence of a small-molecule material, tris(8-hydroxyquinoline) aluminum (Alq3), on bulk heterojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly...In this work, the influence of a small-molecule material, tris(8-hydroxyquinoline) aluminum (Alq3), on bulk heterojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly(2-methoxy-5-(2- ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). By doping Alq3 into MEH-PPV:PCBM solution, the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq3 to MEH-PPV, which probably induces the increase of photocurrent generated by excitons dissociation. However, the low carrier mobility of Alq3 is detrimental to the efficient charge transport, thereby blocking the charge collection by the respective electrodes. The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs. For the case of 5 wt.% Alq3 doping, the device performance is deteriorated rather than improved as compared with that of the undoped device. On the other hand, we adopt Alq3 as a buffer layer instead of commonly used LiF. All the photovoltaic parameters are improved, yielding an 80% increase in power conversion efficiency (PCE) at the optimum thickness (1 nm) as compared with that of the device without any buffer layer. Even for the 5 wt.% Alq3 doped device, the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm (or 2 nm) thermally evaporated Alq3. The performance deterioration of Alq3-doped devices can be explained by the low solubility of Alq3, which probably deteriorates the bicontinuous D-A network morphology; while the performance improvement of the devices with Alq3 as a buffer layer is attributed to the increased light harvesting, as well as blocking the hole leakage from MEH-PPV to the aluminum (Al) electrode due to the lower highest occupied molecular orbital (HOMO) level of Alq3 compared with that of MEH-PPV.展开更多
Donor-acceptor (D-A) type fully conjugated block copolymer systems have been rarely reported due to the challenges in synthetic approaches to prepare well-defined low-polydispersity products. In this work, fully con...Donor-acceptor (D-A) type fully conjugated block copolymer systems have been rarely reported due to the challenges in synthetic approaches to prepare well-defined low-polydispersity products. In this work, fully conjugated block copolymers are synthesized in a one-pot reaction through Stille coupling polycondensation, by utilizing the end-functional polymer copolymerization method. End-functional P3HT are copolymerized with AA (2,7-dihromo-9-(heptadecan-9-yl)-9H- carbazole) and BB (4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole, TBT) type monomers, respectively. The orthogonal solubility between the very soluble P3HT donor and the insoluble PCDTBT acceptor block improves the purity of block copolymers as well as distinct nano-scale phase-separation compared with other reports on miscibility of donor and acceptor polymer block. Further purification via preparative GPC is carried out to remove the excess of unreacted P3HT and free PCDTBT as well as to achieve low polydispersity of block copolymers. The chemical structure of the P3HT- b-PCDTBT block copolymers are verified via IH-NMR, and further confirmed by FTIR spectra. The block copolymer shows broad absorption and moderate optical band gap of 1.8 eV. Furthermore, the fully conjugated block copolymer films exhibit significant fine structures, much smoother film morphology compared to P3HT/PCDTBT polymer blends. By adding a small amount of block copolymer P3HT-b-PCDTBT as a compatibilizer into the bulk-heterojunction of P3HT:PC61BM blends, polymer solar ceils with an 8% increase of short circuit current (Jse) and 10% increase of power conversion efficiency (PCE) are achieved owing to the improvement of the active-layer film morphology. To the best of our knowledge, this is the first report on donor-acceptor type fully conjugated block copolymer as an effective ternary additive in polymer: fullerene bulk heterojunction solar cells.展开更多
OPV (Organic photovoltaic) cells represent a compelling candidate for renewable energy by solar energy conversion. In recent years, versatile light-trapping measures via structures have been intensively explored to ...OPV (Organic photovoltaic) cells represent a compelling candidate for renewable energy by solar energy conversion. In recent years, versatile light-trapping measures via structures have been intensively explored to optimize photovoltaic performance. In this work, a unique rubbing technique is demonstrated to create nanoscale grooves on the PEDOT:PSS [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)] surface and the grating-like features are 500 nm wide and 10 nm deep. The PEDOT:PSS film with grooved surface is used as buffer layers for OPV cell devices based on a P3HT:PCBM bulk heterojunction. The patterned surface has a profound effect on carrier mobility, light trapping, and hole collection efficiency, leading to an increase in the short circuit density, filling factor, and power conversion efficiency. These results indicate the feasibility of the rubbing method can be applicable to high-efficiency OPV cells.展开更多
Efficient bulk heterojunction(BHJ) polymer solar cells with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) hole transfer layer(HTL) were fabricated via controlling the spin coating speed of the HTL...Efficient bulk heterojunction(BHJ) polymer solar cells with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) hole transfer layer(HTL) were fabricated via controlling the spin coating speed of the HTL solution on a particular fluorinated tin oxide substrates of a high roughness.It shows that the functions of the photovoltaic devices increase with the increase of the HTL surface roughness.Then,an imprinting technique was employed to transfer a suitable pattern of nanostructure arrays to the surface of active layers.At the optimized spin coating speed,the photovoltaic devices exhibited a 28.4% increase in efficiency after this imprinting treatment compared with that of nonimprinted photovoltaic devices.It is mainly attributed to the achievement of high interface areas between active layers and electrodes,which not only increases optical absorption by scattering but also facilitates charge carrier collection.展开更多
Under the synergistic effect of molecular design and devices engineering, small molecular organic solar cells have presented an unstoppable tendency for rapid development with putting forward donor- acceptor (D-A) s...Under the synergistic effect of molecular design and devices engineering, small molecular organic solar cells have presented an unstoppable tendency for rapid development with putting forward donor- acceptor (D-A) structures. Up to now, the highest power conversion efficiency of small molecules has exceeded 11%, comparable to that of polymers. In this review, we summarize the high performance small molecule donors in various classes of typical donor-acceptor (D-A) structures and discuss their relationships briefly.展开更多
A novel fused nonacyclic monomer of dithieno[6,5-b:10,11-b']-8 H-cyclopentyl[1,2-b:4,3-b']diphenanthrene(DTCPDP) was synthesized by combining the structural features of ladder-type and multiple fused multi-cycli...A novel fused nonacyclic monomer of dithieno[6,5-b:10,11-b']-8 H-cyclopentyl[1,2-b:4,3-b']diphenanthrene(DTCPDP) was synthesized by combining the structural features of ladder-type and multiple fused multi-cyclic aromatics. DTCPDP has a single sp3-hybridized carbon bridge between fused multi-cyclic aromatics. The copolymerization of DTCPDT with the electron accepting unit of 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole(DTBT) via Stille coupling afforded a novel donor-acceptor(D-A) alternating copolymer PDTCPDT-DTBT. The copolymer exhibited good chemical and thermal stabilities, with an optical band gap of 1.82 eV and a low-lying highest occupied molecular orbital(HOMO) energy level of-5.32 eV. When the copolymer was incorporated into polymer: fullerene(PC_(71)BM) blends to fabricate bulk heterojunction polymer solar cell devices, the devices exhibited a moderate maximum power conversion efficiency(PCE) of 5.90%.展开更多
In this study, we report narrow-size distribution Zn_2SnO_4(ZSO) nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer(EEL) in the inverted polymer solar ce...In this study, we report narrow-size distribution Zn_2SnO_4(ZSO) nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer(EEL) in the inverted polymer solar cells(i-PSCs). Moreover, poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN) is used to modify the surface properties of ZSO thin film. By using the ZSO NPs/PFN as the EEL, the i-PSCs fabricated by poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2-b:4,5-b0] dithio-phene-2,6-diyl-altethylhexyl-3-fluorothithieno [3,4-b]thiophene-2-carboxylate-4,6-diyl](PTB7) blended with(6,6)-phenyl-C_(71)-butyric acid methylester(PC_(71)BM) bulk heterojunction(BHJ) composite, exhibits a power conversion efficiency(PCE) of 8.44%, which is nearly 10% enhancement as compared with that of7.75% observed from the i-PSCs by PTB7:PC_(71)BM BHJ composite using the ZnO/PFN EEL. The enhanced PCE is originated from improved interfacial contact between the EEL with BHJ active layer and good energy level alignment between BHJ active layer and the EEL. Our results indicate that we provide a simple way to boost efficiency of i-PSCs.展开更多
A series of two-dimensional (2D) conjugated copolymers with spatial D-A-D structures (PTNBTB, PTCBTB, and PTSBTB) consisting of hetero-atom-bridged dithiophene and phenylvinyl-substituted benzothiadiazole blocks i...A series of two-dimensional (2D) conjugated copolymers with spatial D-A-D structures (PTNBTB, PTCBTB, and PTSBTB) consisting of hetero-atom-bridged dithiophene and phenylvinyl-substituted benzothiadiazole blocks in the main chain have been designed, synthesized, and characterized. The structure-property relationships of the resulting copolymers were systematically investigated. The effects of the bridging atoms (N, C, and Si) on their thermal, optical, electrochemical and charge- transporting properties were also studied. PTNBTB exhibits a smaller band gap with red-shifted absorption, whereas PTSBTB possesses deeper HOMO level and higher hole mobility than PTCBTB or PTSBTB. Bulk heterojunction (BHJ) solar cells were fabricated and characterized with the conventional configuration of ITO/PEDOT:PSS/copolymer:PCT^BM (I:I)/Ca/A1. As ex- pected, PTSBTB devices showed the highest PCE, up to 4.01%, which was due to the lower HOMO level, higher carrier mobility, and stronger optical response as well as the finer nanoscale phase separation of the pristine polymer and/or the corresponding blending active layer with PC71BM. The primary results offer useful insights in designing 2D copolymers with spatial D-A-D backbone and different hetero-atom bridged donor units to finely tune the absorptions, electronic energy levels, carrier mobilities and the photovoltaic properties.展开更多
文摘The effect of the valence band tail width on the open circuit voltage of P3HT:PCBM bulk heterojunction solar cell is investigated by using the AMPS-1D computer program. An effective medium model with exponential valence and conduction band tail states is used to simulate the photovoltaic cell. The simulation result shows that the open circuit voltage depends Iinearly on the logarithm of the generation rate and the slope depends on the width of the valence band tail. The open circuit voltage decreases with the increasing width of the band tail. The dark and light ideality factors increase with the width of the valence band tail.
基金Project supported by the Natural Science Foundation of Hebei Province,China(Grant No.A2012203016)the Science Fund from the Education Department of Hebei Province,China(Grant Nos.QN20131103 and Z2009114)+1 种基金the Doctor Foundation of Yanshan University,China(Grant No.B580)the Young Teachers’Research Project of Yanshan University,China(Grant No.13LGB028)
文摘We use the method of device simulation to study the losses and influences of geminate and bimolecular recombinations on the performances and properties of the bulk heterojunction organic solar cells. We find that a fraction of electrons(holes)in the device are collected by anode(cathode). The direction of the corresponding current is opposite to the direction of photocurrent. And the current density increases with the bias increasing but decreases as bimolecular recombination(BR)or geminate recombination(GR) intensity increases. The maximum power, short circuit current, and fill factor display a stronger dependence on GR than on BR. While the influences of GR and BR on open circuit voltage are about the same.Our studies shed a new light on the loss mechanism and may provide a new way of improving the efficiency of bulk heterojunction organic solar cells.
基金Supported by the National Natural Science Foundation of China under Grant Nos 21174016 and 11474017the Doctoral Program of Higher Education of China under Grant No 20120009110031
文摘Polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are fabricated by using 1,8-diiodooctane (DIO) as a solvent additive to control the doping density of the PSCs. It is shown that the processing of DIO does not change the doping density of the P3HT phase, while it causes a dramatic reduction of the doping density of the PCBM phase, which decreases the doping density of the whole blend layer from 3.7 × 10^16 cm-3 to 1.2 ×10^16 cm-3. The reduction of the doping density in the PCBM phase originates from the increasing crystallinity of PCBM with DIO addition, and it leads to a decreasing doping density in the blend film and improves the short circuit current of the PSCs.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60978060,10804006,10974013 and 10774013)the Research Fund for the Doctoral Program of Higher Education,China (Grant Nos. 20090009110027 and 20070004024)+5 种基金the Research Fund for the Youth Scholars of the Doctoral Program of Higher Education,China (Grant No. 20070004031)the Beijing Nova Program (Grant No. 2007A024)the Beijing Municipal Natural Science Foundation (Grant No. 1102028)the National Natural Science Funds for Distinguished Young Scholar (Grant No. 60825407)the Beijing Municipal Science & Technology Commission (Grant No. Z090803044009001)the National Basic Research Program of China (Grant No. 2010CB327705)
文摘In this work, the influence of a small-molecule material, tris(8-hydroxyquinoline) aluminum (Alq3), on bulk heterojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly(2-methoxy-5-(2- ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). By doping Alq3 into MEH-PPV:PCBM solution, the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq3 to MEH-PPV, which probably induces the increase of photocurrent generated by excitons dissociation. However, the low carrier mobility of Alq3 is detrimental to the efficient charge transport, thereby blocking the charge collection by the respective electrodes. The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs. For the case of 5 wt.% Alq3 doping, the device performance is deteriorated rather than improved as compared with that of the undoped device. On the other hand, we adopt Alq3 as a buffer layer instead of commonly used LiF. All the photovoltaic parameters are improved, yielding an 80% increase in power conversion efficiency (PCE) at the optimum thickness (1 nm) as compared with that of the device without any buffer layer. Even for the 5 wt.% Alq3 doped device, the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm (or 2 nm) thermally evaporated Alq3. The performance deterioration of Alq3-doped devices can be explained by the low solubility of Alq3, which probably deteriorates the bicontinuous D-A network morphology; while the performance improvement of the devices with Alq3 as a buffer layer is attributed to the increased light harvesting, as well as blocking the hole leakage from MEH-PPV to the aluminum (Al) electrode due to the lower highest occupied molecular orbital (HOMO) level of Alq3 compared with that of MEH-PPV.
基金financially supported by the National Natural Science Foundation of China(No.21304047)Natural Science Foundation of Jiangsu Province(No.13KJB430017)+1 种基金Research Fund for the Doctoral Program of Higher Education(No.20133221120015)Synergetic Innovation Center for Organic Electronics and Information Displays
文摘Donor-acceptor (D-A) type fully conjugated block copolymer systems have been rarely reported due to the challenges in synthetic approaches to prepare well-defined low-polydispersity products. In this work, fully conjugated block copolymers are synthesized in a one-pot reaction through Stille coupling polycondensation, by utilizing the end-functional polymer copolymerization method. End-functional P3HT are copolymerized with AA (2,7-dihromo-9-(heptadecan-9-yl)-9H- carbazole) and BB (4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole, TBT) type monomers, respectively. The orthogonal solubility between the very soluble P3HT donor and the insoluble PCDTBT acceptor block improves the purity of block copolymers as well as distinct nano-scale phase-separation compared with other reports on miscibility of donor and acceptor polymer block. Further purification via preparative GPC is carried out to remove the excess of unreacted P3HT and free PCDTBT as well as to achieve low polydispersity of block copolymers. The chemical structure of the P3HT- b-PCDTBT block copolymers are verified via IH-NMR, and further confirmed by FTIR spectra. The block copolymer shows broad absorption and moderate optical band gap of 1.8 eV. Furthermore, the fully conjugated block copolymer films exhibit significant fine structures, much smoother film morphology compared to P3HT/PCDTBT polymer blends. By adding a small amount of block copolymer P3HT-b-PCDTBT as a compatibilizer into the bulk-heterojunction of P3HT:PC61BM blends, polymer solar ceils with an 8% increase of short circuit current (Jse) and 10% increase of power conversion efficiency (PCE) are achieved owing to the improvement of the active-layer film morphology. To the best of our knowledge, this is the first report on donor-acceptor type fully conjugated block copolymer as an effective ternary additive in polymer: fullerene bulk heterojunction solar cells.
文摘OPV (Organic photovoltaic) cells represent a compelling candidate for renewable energy by solar energy conversion. In recent years, versatile light-trapping measures via structures have been intensively explored to optimize photovoltaic performance. In this work, a unique rubbing technique is demonstrated to create nanoscale grooves on the PEDOT:PSS [poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)] surface and the grating-like features are 500 nm wide and 10 nm deep. The PEDOT:PSS film with grooved surface is used as buffer layers for OPV cell devices based on a P3HT:PCBM bulk heterojunction. The patterned surface has a profound effect on carrier mobility, light trapping, and hole collection efficiency, leading to an increase in the short circuit density, filling factor, and power conversion efficiency. These results indicate the feasibility of the rubbing method can be applicable to high-efficiency OPV cells.
基金Supported by the National High Technology Research and Development Program of China(863Program,2009AA03Z219)the National Basic Research Program of China(973Program,2011CB933300)+1 种基金the National Natural Science Foundation of China(11074194)the Natural Science Foundation of Jiangsu Province(BK2009143)
文摘Efficient bulk heterojunction(BHJ) polymer solar cells with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) hole transfer layer(HTL) were fabricated via controlling the spin coating speed of the HTL solution on a particular fluorinated tin oxide substrates of a high roughness.It shows that the functions of the photovoltaic devices increase with the increase of the HTL surface roughness.Then,an imprinting technique was employed to transfer a suitable pattern of nanostructure arrays to the surface of active layers.At the optimized spin coating speed,the photovoltaic devices exhibited a 28.4% increase in efficiency after this imprinting treatment compared with that of nonimprinted photovoltaic devices.It is mainly attributed to the achievement of high interface areas between active layers and electrodes,which not only increases optical absorption by scattering but also facilitates charge carrier collection.
基金supported by the National Natural Science Foundation of China (Nos. 21474022, 51603051)Youth Innovation Promotion Association CAS and Beijing Nova Program (No. Z171100001117062)the Chinese Academy of Sciences
文摘Under the synergistic effect of molecular design and devices engineering, small molecular organic solar cells have presented an unstoppable tendency for rapid development with putting forward donor- acceptor (D-A) structures. Up to now, the highest power conversion efficiency of small molecules has exceeded 11%, comparable to that of polymers. In this review, we summarize the high performance small molecule donors in various classes of typical donor-acceptor (D-A) structures and discuss their relationships briefly.
基金Funded by the National Natural Science Foundation of China(21673170)
文摘A novel fused nonacyclic monomer of dithieno[6,5-b:10,11-b']-8 H-cyclopentyl[1,2-b:4,3-b']diphenanthrene(DTCPDP) was synthesized by combining the structural features of ladder-type and multiple fused multi-cyclic aromatics. DTCPDP has a single sp3-hybridized carbon bridge between fused multi-cyclic aromatics. The copolymerization of DTCPDT with the electron accepting unit of 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole(DTBT) via Stille coupling afforded a novel donor-acceptor(D-A) alternating copolymer PDTCPDT-DTBT. The copolymer exhibited good chemical and thermal stabilities, with an optical band gap of 1.82 eV and a low-lying highest occupied molecular orbital(HOMO) energy level of-5.32 eV. When the copolymer was incorporated into polymer: fullerene(PC_(71)BM) blends to fabricate bulk heterojunction polymer solar cell devices, the devices exhibited a moderate maximum power conversion efficiency(PCE) of 5.90%.
基金supported by National Natural Science Foundation of China (No. 51329301)
文摘In this study, we report narrow-size distribution Zn_2SnO_4(ZSO) nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer(EEL) in the inverted polymer solar cells(i-PSCs). Moreover, poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN) is used to modify the surface properties of ZSO thin film. By using the ZSO NPs/PFN as the EEL, the i-PSCs fabricated by poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2-b:4,5-b0] dithio-phene-2,6-diyl-altethylhexyl-3-fluorothithieno [3,4-b]thiophene-2-carboxylate-4,6-diyl](PTB7) blended with(6,6)-phenyl-C_(71)-butyric acid methylester(PC_(71)BM) bulk heterojunction(BHJ) composite, exhibits a power conversion efficiency(PCE) of 8.44%, which is nearly 10% enhancement as compared with that of7.75% observed from the i-PSCs by PTB7:PC_(71)BM BHJ composite using the ZnO/PFN EEL. The enhanced PCE is originated from improved interfacial contact between the EEL with BHJ active layer and good energy level alignment between BHJ active layer and the EEL. Our results indicate that we provide a simple way to boost efficiency of i-PSCs.
基金supported by the National Natural Science Foundation of China(20802033,21272164)the National High-Tech R&D Program of China(2013AA031901)+1 种基金the Youth Science and Technology Foundation of Sichuan Province(2013JQ0032)the Fundamental Research Funds for the Central Universities(2012SCU04B01,YJ2011025)
文摘A series of two-dimensional (2D) conjugated copolymers with spatial D-A-D structures (PTNBTB, PTCBTB, and PTSBTB) consisting of hetero-atom-bridged dithiophene and phenylvinyl-substituted benzothiadiazole blocks in the main chain have been designed, synthesized, and characterized. The structure-property relationships of the resulting copolymers were systematically investigated. The effects of the bridging atoms (N, C, and Si) on their thermal, optical, electrochemical and charge- transporting properties were also studied. PTNBTB exhibits a smaller band gap with red-shifted absorption, whereas PTSBTB possesses deeper HOMO level and higher hole mobility than PTCBTB or PTSBTB. Bulk heterojunction (BHJ) solar cells were fabricated and characterized with the conventional configuration of ITO/PEDOT:PSS/copolymer:PCT^BM (I:I)/Ca/A1. As ex- pected, PTSBTB devices showed the highest PCE, up to 4.01%, which was due to the lower HOMO level, higher carrier mobility, and stronger optical response as well as the finer nanoscale phase separation of the pristine polymer and/or the corresponding blending active layer with PC71BM. The primary results offer useful insights in designing 2D copolymers with spatial D-A-D backbone and different hetero-atom bridged donor units to finely tune the absorptions, electronic energy levels, carrier mobilities and the photovoltaic properties.