The effect of a buffer layer on the photovoltaic properties of solar cells with P3OT:fullerene composites

We have studied the effect of buffer layers such as poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), copper phthalocyanine (CuPC), and gold metal on the photovoltaic properties of solar cells with poly(3-octylthiophene) (P3OT):fullerene composites. The device structure is ITO/buffcr/P3OT:C60/BCP/LiF/Al where bathocuproine (BCP) was used as an exciton-blocking layer. The cell with a PEDOT:PSS buffer layer exhibits an open circuit voltage of Voc ∼ 0.4 V and the power conversion efficiency of η ∼ 1.8%. The incident photon to collected election efficiency (IPCE) is about 30% at 520 nm. The cell with a CuPC buffer layer exhibits slightly higher Voc ∼ 0.46 V and power efficiency of η ∼ 2.1%. This result indicates that a good buffer layer at the polymer/electrode interfaces can enhance the Voc. and die power conversion efficiency.