All-inorganic carbon-based CsPbIBr2 perovskite solar cells (PSCs) have attracted increasing interest due to the low cost and the balance between bandgap and stability. However, the relatively narrow light absorption range (300 to 600 nm) limited the further improvement of short-circuit current density (JSC) and power conversion efficiency (PCE) of PSCs. Considering the inevitable reflectance loss (~10%) at air/glass interface, we prepared the moth-eye anti-reflector by ultraviolet nanoimprint technology and achieved an average reflectance as low as 5.15%. By attaching the anti-reflector on the glass side of PSCs, the JSC was promoted by 9.4% from 10.89 mA/cm2 to 11.91 mA/cm2, which is the highest among PSCs with a structure of glass/FTO/c-TiO2/CsPbIBr2/Carbon, and the PCE was enhanced by 9.9% from 9.17% to 10.08%. The results demonstrated that the larger JSC induced by the optical reflectance modulation of moth-eye anti-reflector was responsible for the improved PCE. Simultaneously, this moth-eye anti-reflector can withstand a high temperature up to 200 °C, and perform efficiently at a wide range of incident angles from 40° to 90° and under various light intensities. This work is helpful to further improve the performance of CsPbIBr2 PSCs by optical modulation and boost the possible application of wide-range-wavelength anti-reflector in single and multi-junction solar cells.

Wide-bandgap all-inorganic CsPbIBr2 solar cells with MoOx/Ag/TeO2 composite transparent electrode have been firstly used to construct a 4T perovskite/Si-heterojunction tandem cells. The calculation results showed that the long wavelength transmission (600 to 1100 nm) of MoOx/Ag film can be enhanced remarkably by adding a TeO2 optical capping layer. This resulted in an obviously increase of the PCE (JSC) from 10.70% (17.56 mA/cm 2) to 14.76% (24.67 mA/cm 2) for corresponding bottom Si cell in CsPbIBr2/Si devices, although the PCE of top CsPbIBr2 cell decreased from 17.52% to 16.58%, the overall PCE of tandem device has increased from 28.22% to 31.34%. This JSC-dependent PCE improvement mainly came from the more balanced light absorption, which can be understood by the optical interference induced light field redistributions in CsPbIBr2/Si devices. Specially, comparing with the original Si cell, the JSC and PCE losses in bottom Si cell have been suppressed to about 33% and 32%, which are superior to most the reported pervoskite/Si tandem cells. Therefore, the tandem of Si cell and CsPbIBr2 cell with optimized MoOx(20 nm)/Ag(8 nm)/TeO2(50 nm) transparent electrode could be the promising cost-effective photovoltaic in the future. This work is instructive to the fabrication of pervoskite/Si tandem solar cells.