Benzotriazole(BTA)-based A_(2)-A_1-D-A_1-A_(2)type wide-bandgap(WBG)non-fullerene acceptors(NFAs)have shown promising potential in indoor photovoltaic,and in-depth investigation of their structure-property relationshi...Benzotriazole(BTA)-based A_(2)-A_1-D-A_1-A_(2)type wide-bandgap(WBG)non-fullerene acceptors(NFAs)have shown promising potential in indoor photovoltaic,and in-depth investigation of their structure-property relationship is of great significance.Herein,we explored the chlorination effect of the side chain on the terminals.We introduced Cl atoms into the benzyl side chains in parent BTA5 to synthesize two NFAs,BTA5-Cl with mono-chlorinated benzyl groups and BTA5-2Cl containing bi-chlorinated benzyl groups.We chose D18-Cl with deep-energy levels and strong crystallinity to pair with these three acceptors,affording high photovoltage and photocurrent.With the stepwise chlorination,the open-circuit voltage(V_(OC))values decrease from 1.28,1.22,to 1.20 V,while the corresponding power conversion efficiencies(PCEs)improve from 5.07%,9.15%,to 10.96%.Compared with BTA5-based OSCs,introducing Cl atoms downshifts the energy levels and slightly increases the non-radiative energy loss(0.14<0.17<0.19 e V),resulting in a sequential decrease in VO C.However,more chlorine atom replacements produce more effective exciton dissociation,higher charge transfer,and balanced carrier mobility in the blend films,ultimately achieving better PCEs.This work indicates that chlorination of the benzyl group on the terminals can improve the device's performance,implying good application potential in indoor photovoltaics.展开更多
Organic solar cells(OSCs)have achieved rapid advance due to the continuous development of high-performance key materials.Recently,the power conversion efficiencies(PCEs)of OSCs under 1 Sun condition(AM 1.5 G,100 mW/cm...Organic solar cells(OSCs)have achieved rapid advance due to the continuous development of high-performance key materials.Recently,the power conversion efficiencies(PCEs)of OSCs under 1 Sun condition(AM 1.5 G,100 mW/cm2)are striving toward 19%[1−5].The PCE improvement benefits from the largely enhanced short-circuit current density(Jsc)and fill factor(FF).However,these cells show relatively low open-circuit voltage(Voc)around 0.8-0.9 V.展开更多
Organic solar cells(OSCs)have received great attention for the prominent advantage of low-cost,light-weight and potential for fabricating flexible and semi-transparent device via roll-to-roll printing toward making be...Organic solar cells(OSCs)have received great attention for the prominent advantage of low-cost,light-weight and potential for fabricating flexible and semi-transparent device via roll-to-roll printing toward making better use of inexhaustible renewable clean energy during the past years[1-4].展开更多
High-voltage organic solar cells(OSCs)have received increasing attention because of their promising applications in tandem devices and indoor photovoltaics,but the trade-off between energy loss and charge generation i...High-voltage organic solar cells(OSCs)have received increasing attention because of their promising applications in tandem devices and indoor photovoltaics,but the trade-off between energy loss and charge generation induced by exciton binding energy(E_(b))has become one of the biggest bottlenecks limiting the development of this field.Here,a wide bandgap(WBG)nonfullerene acceptor BTA503 with reduced E_(b) is designed by changing the phenyl side chain on the central core of Cl-BTA5 to an alkyl chain.The diverseπ-πinteractions and enhanced molecular stacking of BTA503 are responsible for its reduced E_(b).Furthermore,both the diminished charge recombination and the fast exciton dissociation caused by the small E_(b) favor the generation of more charge carriers for the PTQ10:BTA503 combination.The efficient Forster resonance energy transfer(FRET)and multiple π-π stacking patterns provide additional charge transfer and transport pathways.Ultimately,the PTQ10:BTA503-based OSC device achieves a V_(OC)of 1.112 V and a PCE of 12.70%,which is higher than that of PTQ10:Cl-BTA5(PCE=10.92%).Simultaneously,the thick film(~300 nm)binary device of PTQ10:BTA503 achieves a PCE of 10.13% with a V_(OC)of 1.102 V,which is the best result for thick film high-voltage OSCs.More importantly,the ternary device of PTQ10:BTA503:Cl-BTA5(1:0.9:0.1)realizes a champion PCE of 13.12% with a V_(OC)of 1.126 V.Our study demonstrates that it is an effective strategy to reduce E_(b) of A_(2)-A_(1)-D-A_(1)-A_(2) type WBG acceptors by modulating the side chains on D unit,which further favors the corresponding devices to obtain world-record PCE and improves their potential for commercial applications.展开更多
For non-fullerene acceptors(NFAs)with linear A_(2)-A_(1)-D-A_(1)-A_(2) backbone,there are three kinds of possible intermolecular interaction,A_(1)-A_(1),A_(1)-A_(2) and A_(2)-A_(2) stacking.Hence,it is a huge challeng...For non-fullerene acceptors(NFAs)with linear A_(2)-A_(1)-D-A_(1)-A_(2) backbone,there are three kinds of possible intermolecular interaction,A_(1)-A_(1),A_(1)-A_(2) and A_(2)-A_(2) stacking.Hence,it is a huge challenge to control this interaction and investigate the effect of intermolecular stacking model on the photovoltaic performance.Here,we adopt a feasible strategy,by utilizing different substituent groups on terminal A2 unit of dicyanomethylene rhodanine(RCN),to modulate this stacking model.According to theoretical calculation results,the molecule BTA3 with ethyl substituent packs via heterogeneous interaction between A_(2) and A_(1) unit in neighboring molecules.Surprisingly,the benzyl group can effectively transform the aggregation of BTA5 into homogeneous packing of A_(2)-A_(2) model,which might be driven by the strong interaction between benzyl and A1(benzotriazole)unit.However,different with benzyl,phenyl end group impedes the intermolecular interaction of BTA4 due to the large steric hindrance.When using a BTA-based D-π-A polymer J52-F as donor according to“Same-A-Strategy”,BTA3-5 could achieve ultrahigh open-circuit voltage(VOC)of 1.17–1.21 V.Finally,BTA5 with benzyl groups realized an improved power conversion efficiency(PCE)of 11.27%,obviously higher than that of BTA3(PCE=9.04%)and BTA4(PCE=5.61%).It is also worth noting that the same trend can be found when using other four classic p-type polymers of P3HT,PTB7,PTB7-Th and PBDB-T.This work not only investigates the intermolecular interaction of A_(2)-A_(1)-D-A_(1)-A_(2) type NFAs for the first time,but also provides a straightforward and universal method to change the interaction model and improve the photovoltaic performance.展开更多
Although fluorination has been proved effective to modulate optoelectronic properties and film morphology,knowledge of managing power conversion efficiency(PCE)and energy loss(Eloss)of organic photovoltaics(OPVs)by se...Although fluorination has been proved effective to modulate optoelectronic properties and film morphology,knowledge of managing power conversion efficiency(PCE)and energy loss(Eloss)of organic photovoltaics(OPVs)by selective fluorination on the donor and/or acceptor is lacking.Herein we designed and synthesized three 1,2,3-benzotriazole(BTA)-based linear polymers(PE45,PE46 and PE47)with different numbers of fluorine atom substitution on the conjugated phenyl side chain.Two classic non-fullerene acceptors(NFAs)Y5(without fluorination)and Y6(with fluorination)were utilized to manage the device efficiency and energy loss.The results revealed that increasing fluorine substitutions on polymer donor improved the OPV efficiencies when the fluorinated Y6 was used as the acceptor,whereas decreased the PCEs when the non-fluorinated Y5 was used as the acceptor.The energy loss declined with the growing fluorine substitutions on polymer donor,and Y5 systems gave the lower values in comparison with the corresponding Y6 cases.It turns out that PE47:Y6 achieved the highest PCE of 15.58%with an open-circuit voltage(VOC)of 0.84 V(Eloss=0.56 e V)due to the highest and balanced hole/electron mobilities,suppressed bimolecular recombination and fibril network morphology,which is the highest value in the BTA-based polymers.Furthermore,PE47:Y5 attained an ultralow non-radiative energy loss of 0.15 e V,which is one of the lowest values among the reported OPVs.Our work could not only give a direct path on how to manage the efficiency and energy loss by selective fluorination on donor and acceptor,but also show a deep understanding on charge generation,transport and collection induced by selective fluorination.展开更多
Spirofluorene （SF） and benzo[d][1,2,3]triazole （BTA） have been considered as promising building blocks to construct n-type photovoltaic materials. Herein, three new small molecule acceptors （SMAs） named BTA21, B...Spirofluorene （SF） and benzo[d][1,2,3]triazole （BTA） have been considered as promising building blocks to construct n-type photovoltaic materials. Herein, three new small molecule acceptors （SMAs） named BTA21, BTA23 and BTA27 with the structure of A2=A1-D-AI^A2 have been designed, in which SF and BTA were used as a central unit of D and bridged acceptor unit of A1, respectively. In addition, 3-ethylrhodanine, 2-（3-ethyl-4-oxothiazolidin-2-ylidene）malononitrile and malononitrile were chosen as terminal acceptor units to modulate the properties of the final SMAs. Three SMAs show wide optical band gaps （Eg） of 2.19, 2.15 and 2.22 eV, respectively, with gradually down-shift of the lowest unoccupied molecular orbital {LUMO） levels in the order of BTAZl, BTA23 and BTA27 depending on the electron-withdrawing capability of terminal acceptor units. BTA21 shows great advantages with respect to donor poly（3-hexylthiophene） （P3HT） over BTA23 and BTA27, such as well energy-level matching, complementary absorption and proper morpholgy, Concequently, P3HT：BTA21 shows the best power conversion efficiency （PCE） value of 3.28% with an open-circuit voltage （Voc） of 1.02 V, a short-circuit current （Jsc） of 5.45 mA.cm-2 and a fill factor （FF） of 0.59. These results indicate that the terminal acceptor group end-capped in SMAs plays a significant role in controlling their optical, electronic, and photovoltaic properties.展开更多
A novel A-D-A （acceptor-donor-acceptor） type non-fullerene small molecule, A201, consisting of an asymmetric thieno[1,2-b]indaceno[5,6-b＇lthienothiophene （TITI＇） unit as middle D part and 2-（3-oxo-2, 3-dihydroi...A novel A-D-A （acceptor-donor-acceptor） type non-fullerene small molecule, A201, consisting of an asymmetric thieno[1,2-b]indaceno[5,6-b＇lthienothiophene （TITI＇） unit as middle D part and 2-（3-oxo-2, 3-dihydroinden-l-ylidene） malononitrile （IC） groups as end-capped A parts was designed and synthesized. The asymmetric TITT building block showed a higher dipole moment of 0.85 Debye （1 Debye = 3.33564 × 10^-3μcm） compared with the symmetric analogues of indacenodithiophene （IDT） and indacenodithieno[3,2-b]thiophene （IDTr） of 0.098 and 0.13 Debye, respectively. The solution-processed bulk heterojunction solar cells using a benzotriazole （BTA）-based polymer of J71 as donor and A201 as acceptor, showed a power conversion efficiency （PCE） of 9.36% with an open-circuit voltage （Voc） of 0.88 V, a short-circuit current Use） of 13.15 mA cm^-2, and a fill factor （FF） of 0.B7, under the illumination of AM 1.5G at 100 mW cm^-2. The high PCE of this material combination could be attributed to its broad absorption spectrum and the high hole mobility （#h） and electron mobility （μh） of 9.56 × 10^-4 and 5.1× 10^-4 cm^2 V^-1 s^-1, respectively. These results indicate that the asymmetric electron-donating segments are promising to construct A-D-A type small molecular acceptors, which could largely enhance the diversity of building blocks to design photovoltaic materials.展开更多
The open-circuit voltage （Voc） of classical photovoltaic polymers, such as P3HT and PTB7-Th, are always restricted when combining with fullerene derivatives, due to the difficulty of modulating the energy levels of ...The open-circuit voltage （Voc） of classical photovoltaic polymers, such as P3HT and PTB7-Th, are always restricted when combining with fullerene derivatives, due to the difficulty of modulating the energy levels of fullerene derivatives. Thus, design of new non-fullerene small molecule acceptor （NFSMA） is very significant to match with these mature polymer donors and improve the Voc and power conversion efficiency （PCE）. Here, a new benzotriazole （BTA）-based NFSMA, BTA7 was synthesized by adopting A2----A1--D--A1--A2 type molecular backbone. By using a strong electron-accepting unit of malononitrile （M） as terminal segment A2, BTA7 demonstrates strong crystallinity, red-shifted absorption spectrum and down-shifted lowest unoccupied molecular orbital （LUMO） energy levels in comparison with BTA1 and BTA2. Organic solar cells （OSCs） based on PTB7-Th：BTA7 realized a high Voc of 1.05 V with a moderate PCE of 4.60%. The energy loss （Eloss = Eg - eVoc） of 0.53 eV is lower than the experiential minimum value of 0.6 eV, which indicates PTB7-Th still has large potential to improve the Voc and photovoltaic performance after the development of novel electron acceptors.展开更多
Poly(3-hexylthiophene)(P3HT)is one of the most used semiconducting polymers for organic photovoltaics because it has potential for commercialization due to its easy synthesis and stability.Although the rapid developme...Poly(3-hexylthiophene)(P3HT)is one of the most used semiconducting polymers for organic photovoltaics because it has potential for commercialization due to its easy synthesis and stability.Although the rapid development of the small molecular non-fullerene acceptors(NFAs)have largely improved the power conversion efficiency(PCE)of organic solar cells(OSCs)based on other complicated p-type polymers,the PCE of P3HT-based OSCs is still low.In addition,the design principle and structure-properties correlation for the NFAs matching well with P3HTare still unclear and need to be investigated in depth.Here we designed a series of NFAs comprised of acceptor(A)and donor(D)units with an A2-A1-D-A1-A2 configuration.These NFAs are abbreviated as Qx3,Qx3 b and Qx3c,where indaceno[1,2-b:5,6-b′]dithiophene(IDT),quinoxaline(Qx)and 2-(1,1-dicyanomethylene)rhodanine serve as the middle D,bridged A1 and the end group A2,respectively.By subtracting the phenyl side groups appended on both IDT and Qx skeletons,the absorption spectra,energy levels and crystallinity could be regularly modulated.When paired with P3 HT,three NFAs show totally different photovoltaic performance with PCEs of 3.37%(Qx3),6.37%(Qx3b)and 0.03%(Qx3 c),respectively.From Qx3 to Qx3b,the removing of phenyl side chain in the middle IDT unit results in the increase of crystallinity and electron mobility.However,after subtracting all the grafted phenyl side groups on both IDT and Qx units,the final molecule Qx3 c exhibits the lowest PCE of only 0.03%,which is mainly attributed to the serious phase-separation of the blend film.These results demonstrate that optimizing the substituted position of phenyl side groups for A2-A1-D-A1-A2 type NFAs is vital to regulate the optoelectronic property of molecule and morphological property of active layer for high performance P3HT-based OSCs.展开更多
基金support from the National Natural Science Foundation of China(Nos.52373176,52073067)。
文摘Benzotriazole(BTA)-based A_(2)-A_1-D-A_1-A_(2)type wide-bandgap(WBG)non-fullerene acceptors(NFAs)have shown promising potential in indoor photovoltaic,and in-depth investigation of their structure-property relationship is of great significance.Herein,we explored the chlorination effect of the side chain on the terminals.We introduced Cl atoms into the benzyl side chains in parent BTA5 to synthesize two NFAs,BTA5-Cl with mono-chlorinated benzyl groups and BTA5-2Cl containing bi-chlorinated benzyl groups.We chose D18-Cl with deep-energy levels and strong crystallinity to pair with these three acceptors,affording high photovoltage and photocurrent.With the stepwise chlorination,the open-circuit voltage(V_(OC))values decrease from 1.28,1.22,to 1.20 V,while the corresponding power conversion efficiencies(PCEs)improve from 5.07%,9.15%,to 10.96%.Compared with BTA5-based OSCs,introducing Cl atoms downshifts the energy levels and slightly increases the non-radiative energy loss(0.14<0.17<0.19 e V),resulting in a sequential decrease in VO C.However,more chlorine atom replacements produce more effective exciton dissociation,higher charge transfer,and balanced carrier mobility in the blend films,ultimately achieving better PCEs.This work indicates that chlorination of the benzyl group on the terminals can improve the device's performance,implying good application potential in indoor photovoltaics.
基金the National Key Research and Development Program of China(2017YFA0206600)the National Natural Science Foundation of China(51773045,21772030,51922032,21961160720,21875052,51873044 and 52073067)the Key Research Program of Frontier Sciences(CAS)(QYZDB-SSW-SLH033).
文摘Organic solar cells(OSCs)have achieved rapid advance due to the continuous development of high-performance key materials.Recently,the power conversion efficiencies(PCEs)of OSCs under 1 Sun condition(AM 1.5 G,100 mW/cm2)are striving toward 19%[1−5].The PCE improvement benefits from the largely enhanced short-circuit current density(Jsc)and fill factor(FF).However,these cells show relatively low open-circuit voltage(Voc)around 0.8-0.9 V.
基金The authors thank the support from the National Key Research and Development Program of China(2017YFA0206600)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZDB-SSW-SLH033)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB36000000)the National Natural Science Foundation of China(NSFC,Nos.21875052,51873044,52073067).
文摘Organic solar cells(OSCs)have received great attention for the prominent advantage of low-cost,light-weight and potential for fabricating flexible and semi-transparent device via roll-to-roll printing toward making better use of inexhaustible renewable clean energy during the past years[1-4].
基金supported by the National Natural Science Foundation of China(21875052,51873044)。
文摘High-voltage organic solar cells(OSCs)have received increasing attention because of their promising applications in tandem devices and indoor photovoltaics,but the trade-off between energy loss and charge generation induced by exciton binding energy(E_(b))has become one of the biggest bottlenecks limiting the development of this field.Here,a wide bandgap(WBG)nonfullerene acceptor BTA503 with reduced E_(b) is designed by changing the phenyl side chain on the central core of Cl-BTA5 to an alkyl chain.The diverseπ-πinteractions and enhanced molecular stacking of BTA503 are responsible for its reduced E_(b).Furthermore,both the diminished charge recombination and the fast exciton dissociation caused by the small E_(b) favor the generation of more charge carriers for the PTQ10:BTA503 combination.The efficient Forster resonance energy transfer(FRET)and multiple π-π stacking patterns provide additional charge transfer and transport pathways.Ultimately,the PTQ10:BTA503-based OSC device achieves a V_(OC)of 1.112 V and a PCE of 12.70%,which is higher than that of PTQ10:Cl-BTA5(PCE=10.92%).Simultaneously,the thick film(~300 nm)binary device of PTQ10:BTA503 achieves a PCE of 10.13% with a V_(OC)of 1.102 V,which is the best result for thick film high-voltage OSCs.More importantly,the ternary device of PTQ10:BTA503:Cl-BTA5(1:0.9:0.1)realizes a champion PCE of 13.12% with a V_(OC)of 1.126 V.Our study demonstrates that it is an effective strategy to reduce E_(b) of A_(2)-A_(1)-D-A_(1)-A_(2) type WBG acceptors by modulating the side chains on D unit,which further favors the corresponding devices to obtain world-record PCE and improves their potential for commercial applications.
基金This work was supported by the National Natural Science Foundation of China(51773046,51673048,21602040)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB36000000)+1 种基金the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(QYZDBSSW-SLH033)the National Key Research and Development Program of China(2017YFA0206600).
文摘For non-fullerene acceptors(NFAs)with linear A_(2)-A_(1)-D-A_(1)-A_(2) backbone,there are three kinds of possible intermolecular interaction,A_(1)-A_(1),A_(1)-A_(2) and A_(2)-A_(2) stacking.Hence,it is a huge challenge to control this interaction and investigate the effect of intermolecular stacking model on the photovoltaic performance.Here,we adopt a feasible strategy,by utilizing different substituent groups on terminal A2 unit of dicyanomethylene rhodanine(RCN),to modulate this stacking model.According to theoretical calculation results,the molecule BTA3 with ethyl substituent packs via heterogeneous interaction between A_(2) and A_(1) unit in neighboring molecules.Surprisingly,the benzyl group can effectively transform the aggregation of BTA5 into homogeneous packing of A_(2)-A_(2) model,which might be driven by the strong interaction between benzyl and A1(benzotriazole)unit.However,different with benzyl,phenyl end group impedes the intermolecular interaction of BTA4 due to the large steric hindrance.When using a BTA-based D-π-A polymer J52-F as donor according to“Same-A-Strategy”,BTA3-5 could achieve ultrahigh open-circuit voltage(VOC)of 1.17–1.21 V.Finally,BTA5 with benzyl groups realized an improved power conversion efficiency(PCE)of 11.27%,obviously higher than that of BTA3(PCE=9.04%)and BTA4(PCE=5.61%).It is also worth noting that the same trend can be found when using other four classic p-type polymers of P3HT,PTB7,PTB7-Th and PBDB-T.This work not only investigates the intermolecular interaction of A_(2)-A_(1)-D-A_(1)-A_(2) type NFAs for the first time,but also provides a straightforward and universal method to change the interaction model and improve the photovoltaic performance.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB36000000)the National Natural Science Foundation of China(21875052,51873044,52073067,21773041,21972031)。
文摘Although fluorination has been proved effective to modulate optoelectronic properties and film morphology,knowledge of managing power conversion efficiency(PCE)and energy loss(Eloss)of organic photovoltaics(OPVs)by selective fluorination on the donor and/or acceptor is lacking.Herein we designed and synthesized three 1,2,3-benzotriazole(BTA)-based linear polymers(PE45,PE46 and PE47)with different numbers of fluorine atom substitution on the conjugated phenyl side chain.Two classic non-fullerene acceptors(NFAs)Y5(without fluorination)and Y6(with fluorination)were utilized to manage the device efficiency and energy loss.The results revealed that increasing fluorine substitutions on polymer donor improved the OPV efficiencies when the fluorinated Y6 was used as the acceptor,whereas decreased the PCEs when the non-fluorinated Y5 was used as the acceptor.The energy loss declined with the growing fluorine substitutions on polymer donor,and Y5 systems gave the lower values in comparison with the corresponding Y6 cases.It turns out that PE47:Y6 achieved the highest PCE of 15.58%with an open-circuit voltage(VOC)of 0.84 V(Eloss=0.56 e V)due to the highest and balanced hole/electron mobilities,suppressed bimolecular recombination and fibril network morphology,which is the highest value in the BTA-based polymers.Furthermore,PE47:Y5 attained an ultralow non-radiative energy loss of 0.15 e V,which is one of the lowest values among the reported OPVs.Our work could not only give a direct path on how to manage the efficiency and energy loss by selective fluorination on donor and acceptor,but also show a deep understanding on charge generation,transport and collection induced by selective fluorination.
文摘Spirofluorene （SF） and benzo[d][1,2,3]triazole （BTA） have been considered as promising building blocks to construct n-type photovoltaic materials. Herein, three new small molecule acceptors （SMAs） named BTA21, BTA23 and BTA27 with the structure of A2=A1-D-AI^A2 have been designed, in which SF and BTA were used as a central unit of D and bridged acceptor unit of A1, respectively. In addition, 3-ethylrhodanine, 2-（3-ethyl-4-oxothiazolidin-2-ylidene）malononitrile and malononitrile were chosen as terminal acceptor units to modulate the properties of the final SMAs. Three SMAs show wide optical band gaps （Eg） of 2.19, 2.15 and 2.22 eV, respectively, with gradually down-shift of the lowest unoccupied molecular orbital {LUMO） levels in the order of BTAZl, BTA23 and BTA27 depending on the electron-withdrawing capability of terminal acceptor units. BTA21 shows great advantages with respect to donor poly（3-hexylthiophene） （P3HT） over BTA23 and BTA27, such as well energy-level matching, complementary absorption and proper morpholgy, Concequently, P3HT：BTA21 shows the best power conversion efficiency （PCE） value of 3.28% with an open-circuit voltage （Voc） of 1.02 V, a short-circuit current （Jsc） of 5.45 mA.cm-2 and a fill factor （FF） of 0.59. These results indicate that the terminal acceptor group end-capped in SMAs plays a significant role in controlling their optical, electronic, and photovoltaic properties.
基金support from the Key Research Program of Frontier Sciences,Chinese Academy of Sciences (QYZDB-SSWSLH033)the National Key Research and Development Program of China (2017YFA0206600)+1 种基金the National Natural Science Foundation of China (51673048,51473040,21504019,51773046,and 21602040)the National Natural Science Foundation of Beijing (2162045)
文摘A novel A-D-A （acceptor-donor-acceptor） type non-fullerene small molecule, A201, consisting of an asymmetric thieno[1,2-b]indaceno[5,6-b＇lthienothiophene （TITI＇） unit as middle D part and 2-（3-oxo-2, 3-dihydroinden-l-ylidene） malononitrile （IC） groups as end-capped A parts was designed and synthesized. The asymmetric TITT building block showed a higher dipole moment of 0.85 Debye （1 Debye = 3.33564 × 10^-3μcm） compared with the symmetric analogues of indacenodithiophene （IDT） and indacenodithieno[3,2-b]thiophene （IDTr） of 0.098 and 0.13 Debye, respectively. The solution-processed bulk heterojunction solar cells using a benzotriazole （BTA）-based polymer of J71 as donor and A201 as acceptor, showed a power conversion efficiency （PCE） of 9.36% with an open-circuit voltage （Voc） of 0.88 V, a short-circuit current Use） of 13.15 mA cm^-2, and a fill factor （FF） of 0.B7, under the illumination of AM 1.5G at 100 mW cm^-2. The high PCE of this material combination could be attributed to its broad absorption spectrum and the high hole mobility （#h） and electron mobility （μh） of 9.56 × 10^-4 and 5.1× 10^-4 cm^2 V^-1 s^-1, respectively. These results indicate that the asymmetric electron-donating segments are promising to construct A-D-A type small molecular acceptors, which could largely enhance the diversity of building blocks to design photovoltaic materials.
基金supported by the National Key Research and Development Program of China (2017YFA0206600)the Key Research Program of Frontier Sciences, Chinese Academy of Sciences (QYZDB-SSW-SLH033)+1 种基金the National Natural Science Foundation of China (51673048, 51473040 and 21602040)the Natural Science Foundation of Beijing (2162045)
文摘The open-circuit voltage （Voc） of classical photovoltaic polymers, such as P3HT and PTB7-Th, are always restricted when combining with fullerene derivatives, due to the difficulty of modulating the energy levels of fullerene derivatives. Thus, design of new non-fullerene small molecule acceptor （NFSMA） is very significant to match with these mature polymer donors and improve the Voc and power conversion efficiency （PCE）. Here, a new benzotriazole （BTA）-based NFSMA, BTA7 was synthesized by adopting A2----A1--D--A1--A2 type molecular backbone. By using a strong electron-accepting unit of malononitrile （M） as terminal segment A2, BTA7 demonstrates strong crystallinity, red-shifted absorption spectrum and down-shifted lowest unoccupied molecular orbital （LUMO） energy levels in comparison with BTA1 and BTA2. Organic solar cells （OSCs） based on PTB7-Th：BTA7 realized a high Voc of 1.05 V with a moderate PCE of 4.60%. The energy loss （Eloss = Eg - eVoc） of 0.53 eV is lower than the experiential minimum value of 0.6 eV, which indicates PTB7-Th still has large potential to improve the Voc and photovoltaic performance after the development of novel electron acceptors.
基金supported by the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(QYZDBSSW-SLH033)the National Key Research and Development Program of China(2017YFA0206600)the National Natural Science Foundation of China(51673048,21875052,51773046,21602040,51873044)
文摘Poly(3-hexylthiophene)(P3HT)is one of the most used semiconducting polymers for organic photovoltaics because it has potential for commercialization due to its easy synthesis and stability.Although the rapid development of the small molecular non-fullerene acceptors(NFAs)have largely improved the power conversion efficiency(PCE)of organic solar cells(OSCs)based on other complicated p-type polymers,the PCE of P3HT-based OSCs is still low.In addition,the design principle and structure-properties correlation for the NFAs matching well with P3HTare still unclear and need to be investigated in depth.Here we designed a series of NFAs comprised of acceptor(A)and donor(D)units with an A2-A1-D-A1-A2 configuration.These NFAs are abbreviated as Qx3,Qx3 b and Qx3c,where indaceno[1,2-b:5,6-b′]dithiophene(IDT),quinoxaline(Qx)and 2-(1,1-dicyanomethylene)rhodanine serve as the middle D,bridged A1 and the end group A2,respectively.By subtracting the phenyl side groups appended on both IDT and Qx skeletons,the absorption spectra,energy levels and crystallinity could be regularly modulated.When paired with P3 HT,three NFAs show totally different photovoltaic performance with PCEs of 3.37%(Qx3),6.37%(Qx3b)and 0.03%(Qx3 c),respectively.From Qx3 to Qx3b,the removing of phenyl side chain in the middle IDT unit results in the increase of crystallinity and electron mobility.However,after subtracting all the grafted phenyl side groups on both IDT and Qx units,the final molecule Qx3 c exhibits the lowest PCE of only 0.03%,which is mainly attributed to the serious phase-separation of the blend film.These results demonstrate that optimizing the substituted position of phenyl side groups for A2-A1-D-A1-A2 type NFAs is vital to regulate the optoelectronic property of molecule and morphological property of active layer for high performance P3HT-based OSCs.
