Evidence for exciton quenching by hole polarons in thick P3HT:PCBM solar cells

摘要

Loss mechanisms near each of the two electrodes of semitransparent solar cells with ZnO and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) contacts are investigated as function of the thickness of the photoactive poly(3-hexylthiophene):methanofullerene (P3HT:PCBM) bulk heterojunction layer (200-500 nm). Varying the intensity of the illumination through the ZnO contact indicates that bimolecular recombination is an important loss mechanism. Illumination through the PEDOT:PSS contact reveals a loss mechanism that is independent of light intensity. Photoluminescence measurements demonstrate that primary P3HT excitons can be quenched by charge carriers that diffuse into the active layer from the PEDOT:PSS contact.