Hysteresis-free perovskite solar cells with compact and nanoparticle NiO for indoor application

The perovskite solar cell technology is showing rapid progress in delivering high power conversion efficiency. This is not limited to conventional 1 SUN illumination, but state-of-the-art results have also been also demonstrated for a low-light condition such as indoor illumination. In this work, we show that very efficient low-light perovskite solar cells can be realized in the inverted configuration with the use of NiO as a hole transporting material by employing a conventional high-temperature process (300 degrees C, compact NiO) or a low-temperature process (<100 degrees C) based on nanoparticle NiO. The power density of 90.2 mu W/cm(2) at 1000 lux was achieved for compact NiO device, while 71.6 mu W/cm(2) was obtained with nanoparticle NiO cells under the same illumination. A detailed electrical, optical, and morphological characterization permitted to identify the reasons for the difference between compact and nanoparticle NiO. Beside the difference in power density, nanoparticle NiO permitted to realize the first low temperature inorganic hole transporting layer for low-light p-i-n perovskite solar cell and, as we show, this could be easily scaled up to 1 cm(2) without suffering for performance losses moving from small to large area.