Journal Article Research Support, Non-U.S. Gov't organic solar cells photostability Polymers Research Support, U.S. Gov't, Non-P.H.S. bulk heterojunction bulk-heterojunction microstructure charge-transfer state high-throughput experimentation low temperature processing machine learning morphology stability nickel oxide non-radiative voltage loss nonfullerene acceptors open-circuit voltage organic photovoltaics perovskite solar cells solar energy