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Thermal-convection-induced defects can cause huge loss in the power conversion efficiency of solution-processed perovskite solar cells. We investigated two types of convection in perovskite solution during the formation of perovskite films. By balancing the convection via special configurations of surface tension and boiling point in mixed γ-butyrolactone (GBL) and dimethylsulfoxide (DMSO), we removed microscopic defects such as rings, bumps, and crevices. The deposited perovskite films were smooth and dense, which enabled a high power conversion efficiency of 17.7% in a 1 cm2 cell area. We believe that the present strategy for controlling the convection can be helpful in improving the perovskite film quality for solvent-rich scalable solution processes of solar cells such as doctor blading, soft-cover deposition, printing, and slot-die coating. [ABSTRACT FROM AUTHOR]

It is of great importance to evaluate the performance of perovskite solar cells (PSCs) accurately, especially to avoid the errors induced by hysteresis during current density–voltage measurement. Here we found that PSCs with n–i–p and p–i–n structures exhibit very different hysteresis behavior. A longer delay time leads to small hysteresis in n–i–p PSCs, whereas it shows little effect in p–i–n ones. In contrast, a smaller voltage step is preferred for reduced hysteresis in p–i–n PSCs, which is further supported by a transient photocurrent study. Finally, we proposed fast and accurate evaluation methods for PSCs based on these two structures. [ABSTRACT FROM AUTHOR]