Highly efficient thermally stable perovskite solar cells via Cs:NiO_x/CuSCN double-inorganic hole extraction layer interface engineering

Obtaining long-term thermally stable via low-cost inorganic-hole extraction layer (i-HEL) is the best choice toward the commercialization of thermo-stable, low-cost perovskite solar cells (PSCs). In the present investigation, we have developed a simple method for p-type cesium incorporated NiO_x (Cs:NiO_x) an active interfacial layer between perovskite and cost-effective CuSCN i-HEL toward thermally stable PSCs. The Cs:NiO_x nanoparticles were synthesized by the simple solution method and spin-coating on to perovskite layer, followed by CuSCN i-HEL deposition for mesoscopic regular (n-i-p) type PSCs. The developed method is not only protecting perovskite layer from polar diethyl sulfide solvent but also extract holes efficiently. The best efficiency based on Cs:NiO_x/CuSCN double-i-HEL devices exhibited 19.24% with >95% thermal stability over 1000 h at 60 °C and >70% at 85 °C thermal air stability over 2000 h. Interestingly, NiO_x/CuSCN and Cs:NiO_x/CuSCN double-i-HEL-based devices are more stable than either conventional spiro-MeOTAD or single-i-HEL-based PSCs due to the perfect isolation of the perovskite layer from polar solvent.