Direct band gap AlPSi3 and GaPSi3 for tandem solar cells

Tandem solar cells with different band gap absorbers have been proven to be an effective way to improve solar cell efficiency. Alloys with the general formula (III–V)1-x(IV2)x are predicted to be direct gap semiconductors, and their wide range of band gaps are expected to be applied to tandem photovoltaics. In this work, we find the Pm-a and Pm-b structures of AlPSi3 using a structure search and then obtain the Pm-a and Pm-b structures of GaPSi3 by atomic substitution. In the synthesis temperature range, all the predicted structures are energetically more favorable than the experimentally synthesized Cc structure of AlPSi3 and GaPSi3, respectively. All the new structures are dynamically stable, with heat resistance up to 1000 K. Compared with the absorption spectra of dia-Si, the Pm-a and Pm-b structures of AlPSi3 and GaPSi3 have higher absorption intensities in the visible range. The Pm-a and Pm-b structures possess direct/quasi-direct band gaps within the optimum range of Shockley−Queisser limit, matching the band gap requirements of the top and bottom cells for double-junction solar cells respectively, thus providing appealing features for applications in tandem solar cells.