Recycling of FTO/TiO₂ Substrates: Route toward Simultaneously High-Performance and Cost-Efficient Carbon-Based, All-Inorganic CsPbIBr₂ Solar Cells

Carbon-based, all-inorganic perovskite solar cells (PSCs) have drawn enormous attention recently on account of their ungraded stability and reduced costs. However, their power conversion efficiencies (PCEs) still lag behind the ones with conventional architecture. Moreover, the high cost of FTO substrates and energy-consuming sintering process of TiO2 electron-transporting layers should be further addressed. Herein, it is demonstrated that the FTO/TiO2 substrates could be separated simply from degraded CsPbIBr2 PSCs for fabricating the new ones again, which thus reduces the production costs of resulting PSCs and makes them renewable and sustainable. Meanwhile, the characterization results reveal that there are some residual CsPbIBr2-derived species on recycled FTO/TiO2 substrates, which enable the upper CsPbIBr2 films with suppressed halide phase separation and reduced defects, the diminished work function of TiO2 layers from 4.13 to 3.89 eV, along with decreased conduction band minimum (CBM) difference of CsPbIBr2/TiO2 interface from 0.51 to 0.36 eV. Consequently, the average PCE of CsPbIBr2 PSCs is improved by 20%, from 6.51 ± 0.62% to 8.14 ± 0.63%, wherein the champion one yields the exceptional value of 9.12%. These findings provide an avenue for simultaneous performance enhancement and cost-saving of carbon-based, all-inorganic PSCs to promote their commercialization.