Influence of phonon-assisted tunneling on photovoltaic properties of BaSi2 and BaGe2 p–n homojunction solar cell devices

Abstract

The solar cell properties of crystalline BaSi2 and BaGe2 p–n homojunctions are explored using density functional theory combined with a nonequilibrium Green function method. In particular, the quantitative estimates of solar cell parameters such as photocurrent, open-circuit voltage (Voc), short-circuit current (|Jsc|), and efficiency (η) are obtained for LDA and GGA-1/2 functionals. The effect of temperature on solar cell parameters is included through electron–phonon coupling (EPC) using the special thermal displacements method. The magnitudes of Jsc, Voc, and η for BaSi2 (BaGe2) at 300 K are found to be 27.35 mA/cm2 (26.1 mA/cm2), 0.84 V (0.78 V), and 18.0% (16.6%), respectively. Our study strongly suggests that the phonon-assisted photon absorption and thereby EPC significantly affect the photocurrent, and its inclusion is necessary for a proper description of various solar cell parameters. The computed solar cell parameters for BaSi2 (BaGe2) p–n homojunctions can be used as benchmark ab-initio quantum mechanical results and can be used in simulations based on continuum models.