Analyzing carrier lifetime of double-layer organic solar cells by using optical electric-field-induced second-harmonic generation measurement

Abstract

By using optical electric-field-induced second-harmonic generation (SHG) measurement, we directly probed charge accumulation and decay processes in double-layer [copper-phthalocyanine (CuPc)/C60] organic solar cells (OSCs). Results showed that negative excess charges accumulated at the CuPc/C60 interface under photoillumination and the charges decayed in a two-step process in dark. Analysis using the filtering method showed that 24% of the accumulated negative excess charges decayed with a lifetime τL1=5.3×10−5 s and the other 76% of charges decayed with a lifetime τL2=6.2×10−2 s. We conclude that analyzing SHG signal response provides a direct way to investigate carrier lifetime in multilayer OSCs.