High Efficiencies in Nanoscale Poly(3-‎Hexylthiophene)/Fullerene Solar Cells

Abstract

<em> 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 with either hydrophobic- or hydrophilic-based copolymers. It was originated from ever increasing trend of fill factor (FF) and increasing or marginally decreasing trend of short circuit current density (J_sc). Although PCEs were higher in untreated hydrophobic-compatibilized devices, the hydrophilic-compatibilized systems further benefited from thermal and solvent treatments. The vertical homogeneity increased for compatibilized BHJs during annealing processes, leading to very high FFs around 70%. The maximum values of Jsc and PCE for the well-controlled photovoltaic systems were 12.10 mA/cm² and 4.85%, respectively.</em>