Gas-Blowing Medicated Aggregation toward 19% Efficiency in Printed Organic Solar Cell from Nonhalogenated Solvent

Doctor-blading is a promising alternative for the large-area printing of organic solar cells (OSCs). However, the power conversion efficiencies (PCEs) of doctor-bladed OSCs are still lower than those of their spin-cast counterparts. This is mainly caused by the prolonged molecular organization time during which excessive aggregation can be encouraged. In this work, a post-treatment using nitrogen gas to blow the backside of the photoactive layer, i.e., the ITO glass side, was utilized to modulate the aggregation growth after blade-coating from a nonhalogenated solvent. A range of morphological measurements reveal that gas-blowing suppresses excessive aggregation of nonfullerene acceptors. As a result, gas-blowing treated PM6:BTP-eC9 OSCs obtained a maximum PCE of 19.0%, which is among the highest values of blade-coated OSCs. Moreover, this morphology transformation also drives the photoactive layer toward the thermodynamic equilibrium state, reducing free volume in the photoactive layer and contributing to better device stabilities.