Efficient and stable inverted polymer solar cells prepared via air exposure

Abstract

The performance of the inverted polymer solar cells (PSCs) were examined with solution-processed TiO2 nanoparticles (TiO2 NPs) as electron transport layer (ETL) and vapor deposited MoO3 as hole transport layer (HTL). The performance of the inverted PSCs based on P3HT:PCBM heterojunction was closely depend on the thickness of interface layer. The high power conversion efficiency (PCE) of 3.90% was achieved when the thickness of MoO3 is 5 nm. The interesting thing is that the PCE of these kinds of inverted PSCs were dramatically enhance after exposing them in air. The increase of the Ag work function, the reduction of MoO3 film work function, and the enlarged P3HT:PCBM grain size are deduced to the main reasons for the improvement of the devices’ performance. The very high PCE of 4.51% was achieved after the device was exposed in air for 144 h. In addition, we also measured the stability of this kind of devices in air for 1008 h. The devices show excellent stability and the PCE of the devices could maintain about 4.0% after 1008 h exposure. The results provide a new facile method for fabrication of highly efficient and stable inverted PSCs.