Passivation of Metal Oxide Surfaces for High-Performance Organic and Hybrid Optoelectronic Devices

Abstract

The exciton quenching properties of solution-processed nickel oxide (NiOx) and vanadium oxide (VOx) are studied by measuring the photoluminescence (PL) of a thin emitting layer (EML) deposited on top of the metal oxides. Strong exciton quenching is evidenced at the metal oxide/EML interface, which is proved to be detrimental to the performance of optoelectronic devices. With a thin polyvinylpyrrolidone (PVP) passivation polymer adsorbed on top of metal oxides, the PL quenching is found to be effectively suppressed. A short UV–O3 treatment on top of the PVP-passivated metal oxides turns out to be a key procedure to trigger the chemical binding between the PVP passivation polymer and the metal oxide surface species, which turns out to be necessary for efficient hole injection and extraction for organic light emitting diodes (OLEDs) and solar cell devices, respectively. With the PVP passivation layer followed by UV–O3 treatment, the OLEDs incorporating NiOx as a hole transport layer (HTL) shows a record current efficiency of 90.8 ± 2.1 Cd A–1 with significantly suppressed efficiency roll-off, the OLEDs incorporating VOx as a hole injection layer (HIL) also shows higher current efficiencies at higher luminescence. Both perovskite solar cells and polymer solar cells incorporating NiOx HTLs show a 60% enhancement in power conversion efficiency (PCE) with PVP passivation polymer.