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

In this work, we present a theoretical study on the use of CuZnSn(S,Se) quantum wells in CuZnSnS 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 CuZnSn(S,Se) without quantum wells is also considered for comparison. CuZnSn(S,Se) 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.