Air-stable, hole-conductor-free high photocurrent perovskite solar cells with CH₃NH₃PbI₃–NiO nanoparticles composite

One of critical issues for practical applications of perovskite solar cells (PSCs) is how to enhance the photocurrent and air stability of the peovskite materials. Here, we report an air-stable, hole-conductor-free (HCF), high photocurrent PSC based on CH₃NH₃PbI₃–NiO nanoparticles (MAPbI₃–NiO NPs) composite. The composite solution contains highly dispersed NiO NPs in solution of CH₃NH₃I(MAI) and PbI₂in dimethylformamide. By introducing the CH₃NH₃PbI₃–NiO composite into the active layer, the HCF-PSCs with FTO/c-TiO₂/mp-TiO₂/MAPbI₃–NiO/Au architecture have been fabricated under ambient conditions. This composite-based HCF-PSCs show a high photocurrent density (J_sc) of 26.41 mA/cm², which is 97%of theoretical maximum (i.e., 27.2 mA/cm²). Compared to the power conversion efficiency (PCE) of MAPbI₃-based HCF-PSC (i.e., 5.43%), the MAPbI₃–NiO NPs composite-based HCF-PSC showed a high PCE of 12.14%. This increase in PCE is mainly due to a remarkable increase in photocurrent density, suggesting that the MAPbI₃–NiO composite enhances the charge carrier generation via improving photo-absorption and fast hole-conduction by NiO NPs. More interestingly, the composite-based HCF-PSCs without encapsulation showed remarkable air stability with retaining ~90% of its original PCE and ~94% of both J_sc and FF for 60 days under ambient environment. XPS and IR spectra analysis revealed that Ni–O, Pb–O, C–O, Ni–N and N–NiO bonds attributed to strong chemical interaction between NiO and MAPbI₃ molecules enhance the air stability of MAPbI₃–NiO composite based HCF-PSCs.