Alumina nanoparticles enable optimal spray-coated perovskite thin film growth on self-assembled monolayers for efficient and reproducible photovoltaics

The power conversion efficiencies of metal halide perovskite photovoltaics have increased rapidly over the past decade attracting significant academic and industrial interest. The ease with which high performance perovskite photovoltaics can be fabricated through solution processing routes has opened up significant possibilities for fabrication through existing, industrially mature high-throughput solution coating techniques such as spray-coating. The power conversion efficiencies of spray-coated metal halide perovskite photovoltaics are limited by non-radiative recombination at the interfaces with charge transport layers necessitating the implementation of new charge transport layers. The self-assembled monolayer (SAM) charge transport layers have resulted in record perovskite photovoltaic device performances, due to reduced non-radiative recombination. However, poor wettability associated with some SAMs significantly limits their applicability, this is exaggerated for droplet-based scalable technologies like spray-coating. Here we report an optimised aluminium oxide nanoparticle interlayer which enables spray-coating of triple cation metal halide perovskite thin films and devices onto Me-4PACz (([4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid). Our interlayer results in improved structural and optoelectronic properties of spray-coated perovskite thin films, compared to those fabricated through spin-coating. These improved properties enable the fabrication of p-i-n photovoltaic devices with efficiencies over 20 % - some of the highest reported for both spray-coated devices in p-i-n architecture, and devices having a spray-coated “triple cation” perovskite active layer.