Analytical Modeling and Optimization of Cu 2 ZnSn(S,Se) 4 Solar Cells with the Use of Quantum Wells under the Radiative Limit.

In this work, we present a theoretical study on the use of Cu 2 ZnSn(S,Se) 4 quantum wells in Cu 2 ZnSnS 4 solar cells to enhance device efficiency. The role of different well thickness, number, and S/(S + Se) composition values is evaluated. The physical mechanisms governing the optoelectronic parameters are analyzed. The behavior of solar cells based on Cu 2 ZnSn(S,Se) 4 without quantum wells is also considered for comparison. Cu 2 ZnSn(S,Se) 4 quantum wells with a thickness lower than 50 nm present the formation of discretized eigenstates which play a fundamental role in absorption and recombination processes. Results show that well thickness plays a more important role than well number. We found that the use of wells with thicknesses higher than 20 nm allow for better efficiencies than those obtained for a device without nanostructures. A record efficiency of 37.5% is achieved when 36 wells with a width of 50 nm are used, considering an S/(S + Se) well compositional ratio of 0.25.