Enhancing the photocurrent in poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester bulk heterojunction solar cells by using poly(3-hexylthiophene) as a buffer layer

This work presents an approach for improving the unfavorable vertical composition gradients of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C-61 butyric acid methyl ester (PCBM) in the photoactive layer of bulk heterojunction solar cells. The proposed method involves simply depositing a thin layer of P3HT on top of poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) prior to the P3HT:PCBM blend is spin coated. The results from photoluminescence and photovoltaic measurements indicate that incorporating this P3HT layer significantly enhances the electron blocking ability of PEDOT:PSS, the efficiency of photoinduced electron transfer and the photocurrent of the device, resulting in an improvement of the power conversion efficiency from 3.98% to 5.05%. (C) 2009 American Institute of Physics. [doi:10.1063/1.3242006]