A Novel Nitrogen-Assisted Method for the Perovskite Active Layer Optimization in the Inverted Planar Heterojunction Perovskite Solar Cells

Abstract

The perovskite solar cells is recognized as a promising candidate for energy industry system because of its tunable band-gap, high absorption coefficient, broad absorption spectrum, high charge carrier mobility and long charge diffusion lengths. However, a dendritic grains morphology, caused by the spin coating procedure, will result in poor coverage and then low power conversion efficiency. In this work, a novel and facile inactive gas assisted method is introduced to obtain uniform and dense perovskite thin films. The dry nitrogen gas blows over the surface of the perovskite solution during the spin-coating process, which promote a faster solvent evaporation. Then, the uniform and compact perovskite film on the substrate was achieved. Typically, the power conversion efficiency (PCE) of the nitrogen gas assisted perovskite solar cells increases from 0.30% to around 9.5 %. Furthermore, the favorable start time of nitrogen blowing on devices was also investigated. The PCE stays around 9.46 % - 9.78 % when the gas starts at 2 sec - 5 sec, and the efficiency decreases to 8.98 % if the gas starts at 6 sec. The nitrogen flow assisted method is proved to be an effective way to fabricate dense perovskite films without polluting the environment.