19% efficiency in organic solar cells of Benzo[1,2-b:4,5-b′]Difuran-based donor polymer realized by volatile + non-volatile dual-solid-additive strategy

Though the application-promising photovoltaic technology named organic solar cells (OSCs) have been close to 20% benchmark power conversion efficiency (PCE) within fabrication friendly single-junction devices, these achievements are enabled by polymer donors based on benzodithiophene cores, requiring toxic production steps. Whilst, the bio-renewable benzo[1,2-b:4,5-b′]difuran unit constructed polymer donors cannot yield comparable efficiency, though their lower steric hindrance is widely appreciated. OSC field has paid great attention on optimizing their performance by chemistry design, yet the device engineering is relatively neglected compared to what have been done on the benzodithiophene side. Here we report a new dual additive strategy of simultaneously applying volatile (2-CN) and non-volatile (MF) solid additives to reduce non-radiative voltage loss and boost charge generation, via an occupying evaporated left vacancies in polymer matrix process. Consequently, the target system D18-Fu:L8-BO's efficiency is promoted to 19.11%, representing the cutting-edge level of this research topic.