NiO x for interface and work function engineering in carbon-based all-inorganic perovskite solar cells.

Carbon-based all-inorganic perovskite solar cells (C-IPSCs) are stable, upscalable and have low CO-footprint to fabricate. However, they are inefficient in converting light to electricity due to poor hole extraction at perovskite/carbon interface. Here we enable an efficient hole extraction in C-IPSCs with the aid of inorganic p-type nickel oxide nanoparticles (NiO-NPs) at the interface and in carbon. By tailoring the work function (WF) of carbon, and reducing the energy-level misalignment at the perovskite/carbon interface, NiO-NPs enable efficient hole transfer, reduce charge recombination and minimize energy loss. As a result, we report 15.01% and 11.02% efficiencies for CsPbIBr and CsPbIBr C-IPSCs, respectively, with a high open-circuit voltage of ∼1.3 V. Unencapsulated interface-modified CsPbIBr devices maintained 92.8% of their initial efficiency at ambient conditions after nearly 2,000 h; and 94.6% after heating at 60 °C for 170 h. This strategy to tailor carbon interface with perovskite offers an important knob in improving C-IPSCs performance.