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

► The electrode charging and the interfacial charging produced electric fields with opposite directions in the C60 layer. ► With increase of external resistance Re, electrode charging was enhanced, while interfacial charging was suppressed. ► The response time of the two charging processes changed similarly as a function of Re. ► The Maxwell-Wagner model well accounted for the results with taking into account the photovoltaic effect.