Journal Article solution processability ternary strategy absorption coefficient all-polymer solar cells all-small molecule organic solar cells batch‐to‐batch insensitivity coating-speed electron acceptors energy loss film thickness green solvent high‐speed coating key performance indexes layer-by-layer processing long-term stability nonradiative recombination organic photovoltaic cells polymerized small molecular acceptors random polymerization strategy scaling lag sequential deposition small molecule acceptor ternary active layer