A modified morphology was introduced for poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) bulk heterojunction (BHJ) solar cells by thermal and solvent annealing treatments in the presence of hydrophilic-hydrophobic block copolymers. Power conversion efficiency (PCE) plummet was prohibited during both thermal and solvent treatments for all BHJ devices modified wit...