Design rules for minimizing voltage losses in high-efficiency organic solar cells

• DOI: 10.1038/s41563-018-0128-z
• Publication Date: 2018-07-12T14:46:19Z
• Authors: Deping Qian; Zilong Zheng; Huifeng Yao; Wolfgang Tress; Thomas R. Hopper; Shula Chen; Sunsun Li; Jing Liu; Shangshang Chen; Jiangbin Zhang; Xiao-Ke Liu; Bowei Gao; Liangqi Ouyang; Yingzhi Jin; Galia Pozina; Irina A. Buyanova; Weimin M. Chen; Olle Inganäs; Veaceslav Coropceanu; Jean-Luc Bredas; He Yan; Jianhui Hou; Fengling Zhang; Artem A. Bakulin; Feng Gao
• Keywords: Technology; Materials Science; RECOMBINATION; Materials Science, Multidisciplinary; Condensed Matter; ENERGY-LOSSES; CHARGE-TRANSFER STATES; DONOR; 01 natural sciences; 7. Clean energy; Physics, Applied; Physical; QUANTUM EFFICIENCY; Nanoscience & Nanotechnology; OPTIMIZATION; HOT; Multidisciplinary; Science & Technology; Chemistry, Physical; Physics; 621; POLYMER; 620; 0104 chemical sciences; Chemistry; Physics, Condensed Matter; Applied; Physical Sciences; SEPARATION; SMALL-MOLECULE ACCEPTOR

The open-circuit voltage of organic solar cells is usually lower than the values achieved in inorganic or perovskite photovoltaic devices with comparable bandgaps. Energy losses during charge separation at the donor-acceptor interface and non-radiative recombination are among the main causes of such voltage losses. Here we combine spectroscopic and quantum-chemistry approaches to identify key rules for minimizing voltage losses: (1) a low energy offset between donor and acceptor molecular states and (2) high photoluminescence yield of the low-gap material in the blend. Following these rules, we present a range of existing and new donor-acceptor systems that combine efficient photocurrent generation with electroluminescence yield up to 0.03%, leading to non-radiative voltage losses as small as 0.21 V. This study provides a rationale to explain and further improve the performance of recently demonstrated high-open-circuit-voltage organic solar cells.