Novel <i>In Situ</i> Self-Doping Cathode Interlayer Materials with Thickness-Insensitivity for High-Efficiency Organic Solar Cells
Haiyang Zhao, Yuejia Dou, Shihao Chen, Haoran Tang, Yuanqing Bai, Ruoxi Tan, Kai Zhang, Chunchen Liu, Fei Huang
Abstract
With the power conversion efficiency (PCE) of single junction organic solar cells (OSCs) surpassing 19%, the development of active layer materials and interlayer materials with thickness-insensitive character becomes crucial for large-area device fabrication. In this study, we synthesized two in situ self-doping cathode interlayer materials, namely PBDPN-Br and PBDPVN-Br, via aldol polycondensation. Compared with PBDPN-Br, PBDPVN-Br, which incorporates ethylene bonds, exhibits enhanced planarity of the conjugated backbone, resulting in improved electron transport capability. When employed as a cathode interlayer in OSCs based on PM6:EH-HD4F, PBDPN-Br and PBDPVN-Br achieved PCEs of 17.59 and 17.89%, respectively. Notably, the PBDPVN-Br-based devices could retain 93% of the initial PCE even though the interlayer thickness was increased to 50 nm, while only 82% of the initial PCE could be retained for PBDPN-Br (50 nm)-based devices. These results highlight the success of regulating the planarity of conjugated backbones for the development of effective thickness-insensitive cathode interlayer materials. Furthermore, when PBDPVN-Br was utilized in OSCs based on the D18:BTP-eC9 active layer, a champion PCE of 18.44% could be achieved, underscoring its competitiveness as a cathode interface material for large-scale processed OSCs.