Impact of Back Surface Field (BSF) Layers in Cadmium Telluride (CdTe) Solar Cells from Numerical Calculation

Abstract

In this study, numerical simulation has been executed using Solar Cell Capacitance Simulator (SCAPS-1D) to study the prospect of favourable efficiency and stable CdS/CdTe cell in various cell configurations. A basic structure of CdS/CdTe cell is studied with 4 µm CdTe as absorber layer, 100 nm tin oxide (SnO2 ) as front contact and 25 nm cadmium sulfides (CdS) as buffer layer. Four back surface fields (BSF) layers namely ZnTe, ZnTe: Cu, Cu2Te and MoTe2 are investigated to reduce the minority carrier recombination at back contact. The cell structure of glass/SnO2 /CdS/CdTe/MoTe2 has shown a nearly ohmic contact with CdTe with the highest efficiency of 17.02% (Voc=0.91 V, Jsc=24.79 mA/cm2 , FF=75.41). Simulation results have verified that MoTe2 as BSF layer is appropriate for an efficient CdS/CdTe cell. Moreover, it is found that a few nanometres (about 40 nm) of BSF layer are enough to achieve high efficiency. For MoTe2 layer, more than 17% efficiency has been achieved compared to other BSF layers.