Recent advances in the use of organic-inorganic hybrid perovskites for optoelectronics have been rapid, with reported power conversion efficiencies of up to 22 per cent for perovskite solar cells. Improvements in stability have also enabled testing over a timescale of thousands of hours. However, large-scale deployment of such cells will also require the ability to produce large-area, uniformly high-quality perovskite films. A key challenge is to overcome the substantial reduction in power conversion efficiency when a small device is scaled up: a reduction from over 20 per cent to about 10 per cent is found when a common aperture area of about 0.1 square centimetres is increased to more than 25 square centimetres. Here we report a new deposition route for methyl ammonium lead halide perovskite films that does not rely on use of a common solvent or vacuum: rather, it relies on the rapid conversion of amine complex precursors to perovskite films, followed by a pressure application step. The deposited perovskite films were free of pin-holes and highly uniform. Importantly, the new deposition approach can be performed in air at low temperatures, facilitating fabrication of large-area perovskite devices. We reached a certified power conversion efficiency of 12.1 per cent with an aperture area of 36.1 square centimetres for a mesoporous TiO-based perovskite solar module architecture.

A uniform and pinhole-free hole-blocking layer is necessary for high-performance perovskite-based thin-film solar cells. In this study, we investigated the effect of nanoscale pinholes in compact TiO2 layers on the device performance. Surface morphology and film resistance studies show that TiO2 compact layers fabricated using atomic layer deposition (ALD) contain a much lower density of nanoscale pinholes than layers obtained by spin coating and spray pyrolysis methods. The ALD-based TiO2 layer acts as an efficient hole-blocking layer in perovskite solar cells; it offers a large shunt resistance and enables a high power conversion efficiency of 12.56%.

Perovskite solar cells are a promising low-cost and highly efficient photovoltaic technology. However, there's still a big challenge in forming large area and uniform perovskite films with a high material utilization ratio. Here we provide a novel continuous processing method, soft-cover deposition, to control the formation of perovskite films in ambient air. High quality films were successfully deposited with less structural defects and high material utilization ratios. Excellent photovoltaic performance was also achieved in a 1 cm 2 unit solar cell, highly reproducible over a large area. The present deposition technology paves the way for future application of high cost-performance perovskite solar cells and the formation of solution processed thin-films.

Ethyl acetate (EA) is introduced in a one-step spin-coating method and can induce instant crystallization of perovskite films to create efficient thermal annealing-free perovskite solar cells.

Large-scale high-quality perovskite thin films are crucial to produce high-performance perovskite solar cells. However, for perovskite films fabricated by solvent-rich processes, film uniformity can be prevented by convection during thermal evaporation of the solvent. Here, a scalable low-temperature soft-cover deposition (LT-SCD) method is presented, where the thermal convection-induced defects in perovskite films are eliminated through a strategy of surface tension relaxation. Compact, homogeneous, and convection-induced-defects-free perovskite films are obtained on an area of 12 cm , which enables a power conversion efficiency (PCE) of 15.5% on a solar cell with an area of 5 cm . This is the highest efficiency at this large cell area. A PCE of 15.3% is also obtained on a flexible perovskite solar cell deposited on the polyethylene terephthalate substrate owing to the advantage of presented low-temperature processing. Hence, the present LT-SCD technology provides a new non-spin-coating route to the deposition of large-area uniform perovskite films for both rigid and flexible perovskite devices.