Temperature-Controlled Slot-Die Coating for Antisolvent-Free-Processed Efficient and Stable Inverted Perovskite Solar Cells

The perovskite solar cells (PSCs) have continued to show their potential as a next-generation power source, achieving record power conversion efficiency (PCE) of over 25% due to their excellent optoelectronic characteristics. However, despite the impressive advances in the PCE to date, most high-performance PSCs are still fabricated with laboratory-scale production (i.e., a spin-coating process associated with anti-solvent dripping), which limits the path to large-area and mass production for commercialization of PSCs. To overcome these issues, it is important to develop high-quality perovskite films in scalable fabrications without spin-coating and/or anti-solvent steps and shift from laboratory scale to industrial scale that guarantees to upscale high-efficiency PSCs.<br/>In this work, for the purpose of practical and scalable fabrication in PSCs, the temperature-controlled slot-die coating method is presented. This concept is further extended to control the solution temperature by using a thermistor-connected slot-die head that releases a hot solution onto a hot substrate. By careful cross-checking the bed and head temperature with coating speeds and its effect on the device performance, it was found that the introduction of the hot head can significantly influence the perovskite film morphology, and a PCE of 17.05 % could be realized at optimized-processing condition (head: 75 °C, bed: 150 °C, coating speed: 3 mm s-1) without spin-coating steps and anti-solvent dripping, which is a higher value than that of the device (12.61 %) without hot head condition. Systematic investigation of device characteristics, film morphologies, and carrier dynamics to reveal the origin of the enhanced PCE shows that the use of the hot-head produces a highly-oriented pinhole-free perovskite morphology with larger and thicker film, which results in enhanced light-harvesting capability, efficient charge carrier transport, and suppressed carrier recombination, leading to the remarkable enhancement in device performance. In addition to the device performance, optimized film condition can also show significant retardation of the decomposition of perovskite films, which lead to long-operation time in the ambient air and thermal condition. Finally, the optimized hot slot-die coating condition is directly utilized to fabricate the scaled device, showing a very close efficiency for spin coating-based PSCs without further modification. As a result, considering the compatibility of slot-die coating that is highly suitable for roll-to-roll (R2R) and sheet-to-sheet line production, hot slot-die coating approaches can provide a simple and useful way to manufacture perovskite films to achieve highly efficient and reliable PSC for industrial purpose