Analyzing interfacial carrier charging in pentacene/C60 double-layer organic solar cells by optical electric field induced second-harmonic generation measurement

Optical electric field induced second-harmonic generation (EFISHG) measurement was applied to investigate interfacial carrier charging in pentacene/C60 double-layer organic solar cells (OSCs) in terms of photovoltaic effect. The EFISHG measurements demonstrated that electrode charging and interfacial charging at the pentacene/C60 interface produce electric fields with opposite directions in the C60 layer. Making use of OSCs connected to various resistances Re showed that the two charging processes exhibit opposite changing tendency due to the photovoltaic (PV) effect, while the response time of the both two charging processes increase with the increases of Re. The Maxwell–Wagner model analysis well accounted for the results obtained using EFISHG measurements.