A systematic study on the optical properties and photovoltaic performance of SnS solar cells using Bethe-Salpeter equation and device simulation

The optical properties of SnS are systematically studied using the Bethe-Salpeter equation (BSE) combined with the GW approximation. Both Haydock algorithm and direct diagonalization algorithm are used to solve the BSE. The first peaks of the dielectric functions along the b-axis has strong excitonic characteristics. The inclusion of the BS kernel leads to important changes in the optical threshold and the amplitudes of the first peaks. The BSE dielectric functions and absorption coefficients are generally in good agreement with experiments. Based on the BSE absorption coefficient and experimental absorption coefficient of SnS, the photovoltaic performance of SnS solar cells was simulated using detailed balance model and AMPS software. The best efficiencies are 31.7 % and 15.9 % for the detailed balance model and AMPS simulation, respectively. The optimum total thickness of SnS absorber layer is 700–1000 nm using AMPS. The influence of defects in the SnS absorbers on the photovoltaic performance of solar cells was also simulated using both lifetime model and DOS model in AMPS in detail. It could be concluded that the improvement of SnS crystal quality (especially, minority-carrier lifetime and carrier mobility) and device transport properties are crucial to further improve the performance of SnS solar cells.