Alkylsilyl Functionalized Copolymer Donor for Annealing-Free High Performance Solar Cells with over 11% Efficiency: Crystallinity Induced Small Driving Force

作者：Huang, Bin; Chen, Lie^*; Jin, Xiufen; Chen, Dong; An, Yongkang; Xie, Qian; Tan, Yun; Lei, Hui; Chen, Yiwang

来源：Advanced Functional Materials, 2018, 28(20): 1800606.

DOI：10.1002/adfm.201800606

• alkylsilyl copolymers
• crystallinity
• energy loss
• polymer solar cells

The contradiction between enlarging the offset between energy levels of donor/acceptor and the required driving force for exciton split leads to a trade-off between open circuit voltage (V-OC) and short circuit current density (J(SC)), which is a big challenge for development of high performance polymer solar cells (PSCs). Some advanced works reported the PSCs with low photon energy loss (E-loss) and small driving force, but the correlation of molecular structures of light-harvesting system and driving force is still unclear. In this work, a new alkylsilyl functionalized copolymer donor PBDS-T (PBDST: poly[(2,6trialkylsilyl thiophen2yl) benzo[1,2b:4,5b'] dithiophene)) alt(5,5(1', 3' di2thienyl5', 7' bis(2ethylhexyl) benzo[1', 2' c:4', 5' c'] dithiophene4,8-dione))]) with low-lying energy levels was designed for efficient PSCs. By monitoring the Photoluminescence quenching of the bulk and bilayer heterojunctions, small driving forces, Delta E-HOMO of 0.15 eV and Delta E-LUMO of 0.22 eV were founded to allow for efficient charge transfer, which were observed to correlate with the crystalline PBDS-T and the optimal morphology in PBDS-T: ITIC (ITIC: 3,9bis-(2methylene(3(1,1dicyanomethylene) indanone)) 5,5,11,11tetrakis(4hexy-lphenyl)-dithieno[2,3d:2', 3' d'] sindaceno[1,2b:5,6b'] dithiophene). Simultaneously improved VOC, JSC and small Eloss boosted the PCE over 11%, which is one of the highest values for annealing-free device. These results shield a light on precise design of a light-harvesting system with small driving force to simultaneously improve the VOC and JSC for highly efficient PSCs.

• 出版日期2018-5-16
• 单位南昌大学