Inorganic nanopillar arrays remarkedly enhance photovoltaic performance of flexible perovskite solar cells

Commercialization of flexible perovskite solar cells (or PSCs) is prohibited by environmental instability and low mechanical robustness. We use glancing angle deposition (GLAD) at low substrate temperature to in-situ deposit nanopillar arrays (NaPAs) onto a flexible electrode for an assembly of flexible PSCs. The NaPAs are made of diverse inorganic materials, such as titanium, titanium oxides, tin oxides (functioning as electron transporting layers) and nickel oxides (serving as hole transporting layers). The as-grown NaPAs enhance light transmittance, facilitate light harvesting in perovskites, promote charge carrier transport and collection, facilitate the formation of large perovskite grains, prohibit perovskites from decomposition, and release mechanic stress. All these features cause large-area flexible PSCs to have PCE of >15%, small photovoltaic hysteresis, 10% degradation for approximately 800-hr storage, and 20% degradation by manual bending for around 400 times.