A Versatile Approach to Organic Photovoltaics Evaluation Using White Light Pulse and Microwave Conductivity

Abstract

State-of-the-art low band gap conjugated polymers have been investigated for application in organic photovoltaic cells (OPVs) to achieve efficient conversion of the wide spectrum of sunlight into electricity. A remarkable improvement in power conversion efficiency (PCE) has been achieved through the use of innovative materials and device structures. However, a reliable technique for the rapid screening of the materials and processes is a prerequisite toward faster development in this area. Here we report the realization of such a versatile evaluation technique for bulk heterojunction OPVs by the combination of time-resolved microwave conductivity (TRMC) and submicrosecond white light pulse from a Xe-flash lamp. Xe-flash TRMC allows examination of the OPV active layer without requiring fabrication of the actual device. The transient photoconductivity maxima, involving information on generation efficiency, mobility, and lifetime of charge carriers in four well-known low band gap polymers blended with phenyl-C₆₁-butyric acid methyl ester (PCBM), were confirmed to universally correlate with the PCE divided by the open circuit voltage (PCE/<i>V</i>_oc), offering a facile way to predict photovoltaic performance without device fabrication