Upscaling of Perovskite Solar Cell Fabrication via Slot-Die Coating: In Situ Tracking of the Drying and Crystallization Front During Gas Quenching

Remarkable progress in efficiency and stability has been demonstrated for the next generation photovoltaic (PV) technology of thin-film perovskite solar cells (PSCs) on the laboratory scale. Small-area PSCs already exceed 25 % of power conversion efficiency (PCE) since they were first investigated about one decade ago [1, 2]. However, besides the unquestionable potential of perovskite-absorber films for efficient thin-film PV, there are significant challenges when scaling the technology. The reason is that established, industrial deposition techniques such as slot-die coating are difficult to control during the entirety of the complex perovskite film formation - causing low operational stability when fabricating larger areas [3]. In response, this work leverages prior studies of our group on a quantitative model of the drying dynamics based on local heat transfer measurements [9], for controlling the crystallization of slot-die coated perovskite absorber layers dried via gas-quenching. More specifically, we apply and validate and this knowledge by systematically implementing and evaluating the upscaling strategy for fabricating slot-die coated modules on an area of 100 cm2 with an elongated slot nozzle. In situ monitoring with a CCD camera is used to critically evaluate the position of the crystallization front on the sample. This position depends directly on the drying dynamics and thus the applied process parameters. Remarkably, we succeed in demonstrating the accurate correlation of the position of the drying front with the evolving thin-film morphology as predicted by the drying models. We further show that these morphological differences have a direct impact on the achievable PCE of perovskite test devices. These methological findings denote a corner stone toward scaling perovskite fabrication preventing expensive brute force optimization. Thus, the transition from perovskite PV to large scale commercially viable manufacturing plants can be significantly facilitated.