Enhancing performance of inverted polymer solar cells by an effective novel double layer combining MoO3 and PEIE

Abstract

Metal oxide of molybdenum oxide (MoO3) and polyethyleneimine ethoxylated (PEIE) was introduced into polymer solar cells (PSCs) as a double interfacial layer. A high power conversion efficiency (PCE) of 3.69% based on poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) was obtained using a MoO3/PEIE bilayer, which is 19.4% higher than that of the pristine devices (the PCE of pristine devices with PEIE interface layer is 3.09%). Results of the analysis via X-ray photoelectron spectroscopy indicated that the MoO3/PEIE bilayer has dual functions. The first function is that MoO3 is successfully transformed into MoO2, enhancing charge transporting. The second function is that the combination of molybdenum oxide and PEIE can be effectively form ohmic contact to reduce interface contact resistance. The measurement of electrochemical impedance and conductivity further illustrated that the MoO3/PEIE double interfacial layer effectively reduced interface contact resistance, promoted charge transport, and enhanced electron transport ability, thereby improving the device performance.