Performance Improvement of Bulk Heterojunction Organic Photovoltaic Cellby Addition of a Hole Transport Material

A novel photovoltaic cell with an active layer of poly(phenyleneethynylene)(PPE)/C₆₀/N,N'-diphenyl-N,N'-di-(m-tolyl)-p-benzidine (TPD) is designed. In the active layer, PPE is the major component; C₆₀ and TPD are the minor ones. Compared with a control BHJ device based on PPE/C₆₀, the short circuitcurrent density J_sc is increased by 1 order of magnitude, and the whole device performance is increased greatly, however the open circuit voltage V_oc is largely decreased. The possible mechanism of the improved performance may be as follows: In the PPE/C₆₀/TPD device, PPE, C₆₀, and TPD serve as the energy harvesting material, the electron transport material, and the holetransport material, respectively. As the TPD and C₆₀ are spatially separated by PPE, the charge recombination is effectively retarded.