Understanding Coating Thickness and Uniformity of Blade-Coated SnO2 Electron Transport Layer for Scalable Perovskite Solar Cells

Abstract

The low-cost and fully solution-based perovskite photovoltaic devices can be upscaled by using the blade coating method. However, control of the charge transport layers thickness on nanometer scale is challenging since the inherent nature of the blade coating process unavoidably induces thickness gradients along the coating direction of blade coated layer. Herein, the film thickness and the uniformity of blade-coated SnO2 colloidal dispersions in the Landau–Levich regime are systematically studied by varying the substrate temperature, the dispensed solution volume, and the solution concentration as well as the coating speed. It is shown that the advancing meniscus height heavily influences the SnO2 film thickness. As the solution is consumed during the coating process, the meniscus height decreases and hence the film thickness, yielding poor uniformity of the blade-coated layer. To improve the thickness uniformity, the dispensed solution volume is used to reduce the alteration of the advancing meniscus height along the coating direction and minimize the capillary flow with the appropriate substrate temperature. This study provides crucial insights toward the successful upscaling of perovskite solar cells by blade coating.