Journal Article organic solar cells power conversion efficiency small-molecular acceptors B←N bond active layer all-inorganic perovskites all-polymer solar cell all-polymer solar cells benzo[1,2-b:4,5-b′]difuran charge transfer device performance device stability electron-deficient unit hole-transporting materials homo-tandem inverted perovskite solar cells isomeric end groups isomeric solid additives mild post-treatment non‐radiative loss passivation effect polymer acceptor polymer acceptors recombination layers reverse thermal annealing small-molecule acceptors voltage loss