18% High‐Efficiency Air‐Processed Perovskite Solar Cells Made in a Humid Atmosphere of 70% RH (Solar RRL 9∕2017). Issue 9 (6th September 2017) - Cheng, Yuanhang
Abstract : To realize high‐efficiency air‐processable perovskite solar cells (PVSCs), understanding the impact of ambient conditions on the formation of the light absorber perovskite materials is of the utmost importance. Herein, Cheng et al. (article No.201700097 ) have found that the moisture in air rapidly accelerates the crystallization of the precursor materials and leads to an uncontrollable film morphology. More importantly, for the first time, it is found that the oxygen in air significantly reduces the wettability of the precursor solution on substrate and results in a non‐continuous thin film. The two limiting factors can be eliminated by simply escalating the deposition temperture, through which a fully covered and uniform precursor thin films in air was achieved, even at humidity as high as 70%. It is proposed that such improvement is due to the increased vapor pressure of the solvent at higher temperature to reduce the ingress of oxygen and moisture into the precursor materials during the solution deposition process. By further optimizing the deposition temperature, air‐processed PVSCs with a champion efficiency of 18.1% under a high humidity environment of 70% RH was achieved.