Enhancing the open circuit voltage of PEDOT:PSS-PC61BM based inverted planar mixed halide perovskite solar cells from 0.93 to 1.05 V by simply oxidizing PC61BM

In this paper we propose a simple method of oxidization of PC61BM, which is commonly used in perovskite solar cells as the electron transport layer, to enhance the open circuit voltage (V-oc) of PEDOT:PSS-PC61BM based inverted planar mixed halide perovskite solar cells. By simply oxidizing PC61BM, the V-oc was enhanced from 0.93 to 1.05 V. The power conversion efficiency thus was increased from 14.22% to 16.45%. This improvement is attributed to the lower charge carrier recombination rate and faster charge transfer at the interface after oxidation PC61BM layer, as revealed by time resolved photoluminescence, transient photovoltage and transient photocurrent measurements. Ultra-violet photoelectron spectroscopy measurements indicate about 0.12 V shift of the work function of PC61BM after oxidation, supporting the above conclusion.