Rapid route to efficient, scalable, and robust perovskite photovoltaics in air
We demonstrate a scalable atmospheric plasma route to rapidly form efficient and mechanically robust photoactive metal halide perovskite films in open air at linear deposition rates exceeding 4 cm s−1. Our plasma process uses clean dry air to produce a combination of reactive energetic species (ions, radicals, metastables, and photons) and convective thermal energy to rapidly convert the perovskite precursor solution after spray-coating. Such high energy species dissociate the precursor and superheat the solvent, quickly and efficiently curing the perovskite film. Synchrotron X-ray radiation enabled in situ wide angle X-ray scattering (WAXS) measurements with high time resolution. The ultrafast crystallization kinetics are governed by rapid nucleation and growth during the plasma exposure, followed by continued grain growth during cooling. We deposit pinhole-free, robust CH3NH3PbI3 films with a ten-fold increase in fracture toughness, a key metric for reliability. Planar devices exhibited remarkably consistent performance with 15.7% power conversion efficiency (PCE) without hysteresis and an improved open-circuit voltage (VOC). This excellent performance is attributed to lower defect densities, as measured by external quantum efficiency, steady-state and time-resolved photoluminescence. Large-area devices were made with a strip of 10 samples, and a 13.4% average PCE was measured on a total of 2.4 cm2 electrode area.