Defect-Induced Loss Mechanisms in Polymer–Inorganic Planar Heterojunction Solar Cells

The effect of ZnO defects on photoexcited charge carrier recombination and forward induced charge transfer was studied in organic-inorganic bilayer organic heterojunction solar cells. Decreased bimolecular recombination via passivation of ZnO nanopariticle defects resulted in longer carrier lifetime as determined by transient photovoltage (TPV) measurements. It was also found by time-resolved photoluminescence (TRPL) measurements that defect passivation decreased the fluorescence lifetime which indicated higher exciton dissociation efficiency. Through passivation of the ZnO nanoparticles defects, the two loss mechanisms were reduced and the power conversion efficiency (PCE) is significantly enhanced.