Transition metals doped CuAlSe2 for promising intermediate band materials

TL;DR

This study explores transition metal doping in CuAlSe2 to create intermediate bands, enhancing solar cell efficiency by improving optical absorption, with Ti doping identified as the most promising candidate.

Contribution

It systematically analyzes the stability and electronic properties of transition metal doped CuAlSe2, revealing Ti doping as optimal for intermediate band formation.

Findings

Ti-doped CuAlSe2 has a half-filled intermediate band.

Doping stabilizes only when Al is substituted.

Enhanced optical absorption observed with Ti doping.

Abstract

Introducing an isolated intermediate band (IB) into a wide band gap semiconductor can potentially improve the optical absorption of the material beyond the Shockley-Queisser limitation for solar cells. Here, we present a systematic study of the thermodynamic stability, electronic structures, and optical properties of transition metals (M = Ti, V, and Fe) doped CuAlSe2 for potential IB thin film solar cells, by adopting the first-principles calculation based on the hybrid functional method. We found from chemical potential analysis that for all dopants considered, the stable doped phase only exits when the Al atom is substituted. More importantly, with this substitution, the IB feature is determined by $3d$ electronic nature of M^{3+} ion, and the electronic configuration of 3d^1 can drive a optimum IB that possesses half-filled character and suitable subbandgap from valence band or conduction band. We further show that Ti-doped CuAlSe2 is the more promising candidate for IB materials since the resulted IB in it is half filled and extra absorption peaks occurs in the optical spectrum accompanied with a largely enhanced light absorption intensity. The result offers a understanding for IB induced by transition metals into CuAlSe2 and is significant to fabricate the related IB materials.