Charge dynamics in solar cells with a blend of π-conjugated polymer-fullerene studied by transient photo-generated voltage

Abstract

The biphasic feature of transient photo-generated voltage (TPV) is investigated in organic solar cells (OSCs) with a blend active layer of poly(3-hexylthiophene) (P3HT) and phenyl C61 butyric acid methyl ester (PCBM). The positive and negative components in biphasic TPV are explained through PCBM only and P3HT only devices. The negative and positive components are ascribed to the dipole formation at the buried interface of P3HT/indium tin oxide (ITO) and PCBM/ITO respectively. Based on these findings, two fundamental phenomena are revealed as follows: (1) interfacial modification on the buried interface inverts the negative component in biphasic TPV to a positive component, which prevents the leakage current channel in the conventional OSC structure; and (2) the solvent chosen transforms the positive component in biphasic TPV into a negative signal, which blocks the leakage current channel in the inverted OSC structure. Consequently, the study of TPV polarity provides the justification of the interaction at the buried interface. Besides, the decay of TPV is found to be bi-exponential, which can be used as a tool to estimate the degree of charge balance in OSCs.

Room-temperature solution-processed molybdenum oxide as a hole transport layer with Ag nanoparticles for highly efficient inverted organic solar cells

“…† This indicates that the carrier will transfer faster through the Ag NP-MoO x composite lm to the anode than that of the pristine MoO x and evaporated MoO 3 lms. 47 It should be noted that the hole dominated device and TPV measurement of the OSCs with the solution-processed MoO x lm overlap with those of the evaporated MoO 3 lm. This re-conrms that the room-temperature solution-processed MoO x lm functions as good as the evaporated MoO 3 lm as described before.…”