Sn(II)-containing phosphates as promising p-type optoelectronic semiconductors*

High-performance and stable p-type optoelectronic semiconductors, such as transparent conductors, have been searched for with decades of efforts. We herein proposed based on first-principles straightforward calculations and structure searches Sn(II)-containing phosphates Sn_nP₂O_5+n (n=2, 3, 4, 5, …) as promising p-type semiconductors for optoelectronic applications. We found that these materials have large band gaps and can have moderate effective masses for both holes and electrons. Calculations of optical properties show that interband transitions in the visible are weak under hole doping. We also find an interesting inverse Burstein-Moss shift, which can be understood in terms of the Sn character of both the states at band edges. By investigating intrinsic defects properties, we identified dominant carrier traps and revealed ideal growth conditions for p-type Sn(II) phosphates. The results indicate that Sn_nP₂O_5+n with large n may be doped to p-type with promising attainable hole density. The unusual combinations of relatively high band gap, low carrier masses and high chemical stability suggest possible optoelectronic applications of Sn(II) phosphates.