Enhanced open-circuit voltage in methoxyl substituted benzodithiophene-based polymer solar cells  

作　　者：Xiaonan Xue Yao Liu Xiangyi Meng Xiaobo Sun Lijun Huo Wei Ma Yanming Sun 

机构地区：[1]School of Chemistry and Environment, Beihang University, Beijing 100191, China [2]Heeger Beijing Research and Development Center, Beihang University, Beijing 100191, China [3]State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China

出　　处：《Science China Chemistry》2017年第2期243-250,共8页中国科学（化学英文版）

基　　金：supported by the National Natural Science Foundation of China(51273203,51261160496,51473009, 21504066);the International Science & Technology Cooperation Program of China(2014DFA52820);the Ministry of Science and Technology (2016YFA0200700);the Fundamental Research Funds for the Central Universities(YWF-14-HXXY-014,YWF-15-HHXY-003)

摘　　要：The open-circuit voltage(V_(oc))is one of the important parameters that influence the power conversion efficiency(PCE)of polymer solar cells.Its value is mainly determined by the energy level offset between the highest occupied molecular orbital(HOMO)of the donor and the lowest unoccupied molecular orbital(LUMO)of the acceptor.Therefore,decreasing the HOMO value of the polymer could lead to a high V_(oc)and thus increasing the cell efficiency.Here we report a facile way to lower the polymer HOMO energy level by using methoxyl substituted-benzodithiophene(BDT)unit.The polymer with the methoxyl functionl group(POBDT(S)-T1)exhibited a HOMO value of-5.65 eV,which is deeper than that(-5.52 eV)of polymer without methoxyl unit(PBDT(S)-T1).As a result,POBDT(S)-T1-based solar cells show a high V_(oc)of 0.98 V and PCE of 9.2%.In contrast,PBDT(S)-T1-based devices show a relatively lower V_(oc)of 0.89 V and a moderate PCE of 7.4%.The results suggest that the involvement of methoxyl group into conjugated copolymers can efficiencly lower their HOMO energy levels.The open-circuit voltage（V_（oc））is one of the important parameters that influence the power conversion efficiency（PCE）of polymer solar cells.Its value is mainly determined by the energy level offset between the highest occupied molecular orbital（HOMO）of the donor and the lowest unoccupied molecular orbital（LUMO）of the acceptor.Therefore,decreasing the HOMO value of the polymer could lead to a high Voc and thus increasing the cell efficiency.Here we report a facile way to lower the polymer HOMO energy level by using methoxyl substituted-benzodithiophene（BDT）unit.The polymer with the methoxyl functionl group（POBDT（S）-T1）exhibited a HOMO value of-5.65 eV,which is deeper than that（-5.52 eV）of polymer without methoxyl unit（PBDT（S）-T1）.As a result,POBDT（S）-T1-based solar cells show a high V（oc of 0.98 V and PCE of 9.2%.In contrast,PBDT（S）-T1-based devices show a relatively lower Voc of 0.89 V and a moderate PCE of 7.4%.The results suggest that the involvement of methoxyl group into conjugated copolymers can efficiencly lower their HOMO energy levels.

关 键 词：polymer solar cell conjugated polymer HOMO open-circuit voltage power conversion efficiency 

分 类 号：TM914.4[电气工程—电力电子与电力传动] O626.12[理学—有机化学]