A 'Smart-Bottle' humidifier-assisted air-processed CuSCN inorganic hole extraction layer towards highly-efficient, large-area and thermally-stable perovskite solar cells

A long-term thermally stable, inexpensively produced, inorganic-hole extraction layer (i-HEL) is the best choice for the commercialization of air-thermo-stable, low-cost, highly-efficient perovskite solar cells (PSCs). Low-cost, thermally-stable inorganic copper(i) thiocyanate (CuSCN) i-HEL is the best choice. However, it has unique solubility in polar diethyl sulfide solvent and the conventional spin-coating method damages the perovskite layer, hampering large-area fabrication. In the present investigation we have developed a novel, simple smart-bottle-humidifier-assisted (SBHA) method for p-type CuSCN i-HEL deposition towards air-thermally stable low-cost PSCs. The developed method is very simple, ambient-air processed, cheap and could be suitable for large-area deposition. The best efficiency based on CuSCN i-HEL devices exhibited was 18.78% with >95% and >85% thermal stability over 1000 hours, respectively at 65 ± 1 and 85 ± 1 °C. Interestingly, CuSCN i-HEL-based devices show >2000 hours of air-stability and are much more stable than conventional expensive additive-doped spiro-MeOTAD-based PSCs. We also explored this technique for large-area (∼1.04 cm²) fabrication and it exhibited 18.34% PCE with >85% thermal stability at 85 ± 1 °C over 1000 hours, revealing that the developed method is also suitable for large-area perovskite fabrication.