Exploring the n-GaN films with Cs coating surface for low work function solar cell anode

Abstract

In this study, the first principle calculation is utilized to investigate the possibility of GaN to be applied as the anode of solar cells based on photon-enhanced thermionic emission (PETE). The results suggest that Si-doped GaN(0001) surface can obtain satisfactory ionization in N-rich environment. Substituted atoms are inclined to replace Ga atoms in the outmost layer. The highest carrier concentration is obtained when substitutional atoms are in the first bilayer. Surface coating technology utilizing Cs adatoms can effectively modify the surface work function. The optimal adsorption site on GaN(0 0 0 1) surface is N-top site. The work function attains the minimum at 0.75 ML coverage as multiple Cs atoms adsorbed. Simultaneously, the conversion efficiency reaches a peak value of 37% at 0.75 ML Cs coverage according to the theoretical prediction. Besides, the conversion efficiency largely depends on the temperature when the work function of the anode is low enough (at least lower than 1 eV). Our results demonstrate the possibility of GaN as the anode of PETE devices and provides a method for discovering more candidate materials for both the cathode and anode.