Fully Dry-Processed and Powder-Based Halide Perovskite Solar Cells by Powder-Aerosol-Deposition and Hot-Pressing

The lifetime and stability of halide perovskite solar cells is well known to be reduced by high internal strain, which correlates with a high degree of energetic disorder. Here, we present a novel method to prepare perovskite solar cells with a low level of internal strain and disorder using a fully dry processing approach suitable for upscaling.<br/>For this, we first prepared perovskite powder with remarkable stability by dry mechanochemical synthesis. Subsequently, this powder is deposited by a dry powder-aerosol-deposition method and pressed at elevated temperatures. This hot-pressing approach increases the grain size and reduces the disorder and strain in the films. Strain and disorder are analyzed using XRD as well as detailed Urbach analyses of temperature dependent photoluminescence and absorption spectra. These detailed Urbach analyses enable us to accurately determine even low static disorder values. We find values as low as 3.7 meV for the dry-processed, pressed films. Moreover, hot-pressing improves the surface roughness and compactness of the films to such an extent that their integration into a solar cell configuration becomes feasible. We demonstrate fully working dry-processed powder-based perovskite solar cells - the first of their kind.<br/>The solvent-free approach allows to separately optimize the synthesis of the material, and the processing of the film. This contrasts with the currently used approaches where the perovskite forms only as the film is formed. Our results thus pave the way for a novel fabrication method of thin-film perovskite solar cells that is suitable for upscaling and that has strong potential to advance the stability of perovskite-based devices.