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

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 ) / C 60 ] organic solar cells (OSCs). Results showed that negative excess charges accumulated at the CuPc / C 60 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 τ L 1 = 5.3 × 10 − 5 s and the other 76% of charges decayed with a lifetime τ L 2 = 6.2 × 10 − 2 s . We conclude that analyzing SHG signal response provides a direct way to investigate carrier lifetime in multilayer OSCs.