Disruptive Durable All-Polymer Solar Cells (FY2019-000119-AS)

To date, light-weight, flexible bulk-heterojunction polymer solar cell (BHJ-PSC) advances have been dominated by polymer donor + fullerene acceptor blend active layers. However this situation has changed dramatically with the advent of specific classes of non-fullerene molecular acceptors, and cell performance metrics such as power conversion efficiencies (PCEs) have soared to ~16% (literature projected: 20-25%) with 17% recently achieved by these Pis at Northwestern U. (NU). Nevertheless, polymer-small molecule blend photovoltaic structures have intrinsic morphological, thermodynamic, environmental, and mechanical instabilties and weaknesses. In contrast, all-polymer solar cells (APSCs) based on donor polymer + acceptor polymer blends have received far less attention and offer many untapped advantages. To date, PCEs have recently surpassed (by a small amount) the 10% benckmark and the NU team has already achieved ~ 9%. Moreover, fundamental polymer science and these initial results argue that, if curent materials synthesis and processing challenges are addressed, APSCs will provide: 1) High, tunable light absorption; 2) High PCEs and other photovoltaic metrics, perhaps equalling those of polymer donor + fullerene acceptor blends; 3) Robust BHJ film morphologies; 4) Long-term thermal, oxidative, and mechanical stability; 5) Compatibility with environmentally benign large module manufacture. To advance APSCs to the next level and achieve these objectives will require an integrated synthesis, processing, and characterization effort integrating three tasks: Task 1. Synthesize new block copolymer acceptors. The objectives of this task are: (i) Achieve good miscibility with retention of polymer transport characteristics; (ii) Use quinoidal polymer blocks to enhance light harvesting, with the best structures to be prepared in di/triblock versions. (iii) The most promising acceptors from I and ii will be refined by 2D molecular mass mapping, then transitioned to module fab