P-Type Nb-Doped MoS2 Layer for Solar Cell Application

Abstract

Herein, under a H2S/Ar ambient, a p+-type Nb-doped MoS2 (MoS2:Nb) film is developed via a sulfurization for a cosputtered Mo–Nb metal precursor to be applied to chalcogenide thin-film solar cells. With the [Nb]/([Nb] + [Mo]) compositional ratio, the surface roughness and growth rate increase with the domination and diminishment of the (100) and (002) planes, respectively. By increasing the [Nb]/([Nb] + [Mo]) compositional ratio from 0 to 0.06, simultaneously, the carrier density of the MoS2:Nb films increases from 2.9 × 1016 up to 3.7 × 1020 cm−3, and the conductivity type changes from n-type to p-type as a result of the Nb atoms acting as acceptors. The ionization energy indicates a transition from a broad Nb acceptor band to a vacuum level for the highly doped p-type MoS2:Nb films. Thus, by utilizing the p+-type MoS2:Nb intermediate layer in the chalcogenide solar cells, a suppressed carrier recombination at the Mo back electrode/chalcogenide absorber interface by a back surface field is expected. Overall, it is believed that the obtained findings in this work can help boost the power conversion efficiency of the chalcogenide solar cells owing to the back junction modification.