High shunt resistance in polymer solar cells comprising a $MoO3$ hole extraction layer processed from nanoparticle suspension

In this report, we present solution processed molybdenum trioxide $(MoO3)$ layers incorporated as hole extraction layer (HEL) in polymer solar cells (PSCs) and demonstrate the replacement of the commonly employed poly(3,4-ethylene dioxythiophene):(polystyrene sulfonic acid) (PEDOT:PSS). $MoO3$ is known to have excellent electronic properties and to yield more stable devices compared to PEDOT:PSS. We demonstrate fully functional solar cells with up to 65 nm thick $MoO3$ HEL deposited from a nanoparticle suspension at low temperatures. The PSCs with an active layer comprising a blend of poly(3-hexylthiophene) and [6,6]-phenyl-$C61$ butyric acid methyl ester and a $MoO3$ HEL show comparable performance to reference devices with a PEDOT:PSS HEL. The best cells with $MoO3$ reach a fill factor of 66.7% and power conversion efficiency of 2.92%. Moreover, $MoO3$ containing solar cells exhibit an excellent shunt behavior with a parallel resistance of above $100kΩcm2$⁠.