Ag-alloying enables wide-bandgap (1.69 eV) chalcopyrite solar cell with 11.5% efficiency and over 900 mV open circuit voltage from molecular solution

Development of wide-bandgap solar cells is important to expand the application scenarios of photovoltaic. Pure sulfide chalcopyrite Cu(In,Ga)S₂ (CIGS) with high stability are ideal absorber materials for these applications. The CIGS are mostly fabricated from vacuum-method with low-bandgap (&lt; 1.65 eV) or poor performance. Here, we fabricate wide-bandgap CIGS from molecular solution through cost-effective scalable doctor-blading technique. Results show the performance of intrinsic CIGS is limited by low crystallinity. Ag is incorporated in CIGS by substitution of Cu in the solution, which improves film crystallinity and reduces defect concentration. Further, Ag-alloying lowers CIGS energy-band without changing bandgap, decrease conduction band offset at the heterojunction. The greatly reduced charge carrier recombination and charge transfer resistance lead to CIGS solar cell with an efficiency of 11.5% and an open circuit voltage (<em>V</em><em>_OC</em>) of 904 mV with a bandgap of 1.69 eV, the highest efficiency and lowest <em>V</em>_OC loss of wide-bandgap CIGS solar cell.