High performance ultra-thin CdTe solar cell with Lead Telluride BSF

Abstract

The polycrystalline cadmium telluride (CdTe) is a leading photovoltaic (PV) material for the possibility of high-efficiency and low-cost thin film solar cell. The absorber material CdTe has a high absorption coefficient over 5×10 5 /cm and it has a direct bandgap of 1.45 eV, which is very close to the optimum bandgap for solar cells. In this work, numerical analysis was done utilizing AMPS (Analysis of Microelectronic and Photonic Structures) simulator to investigate the possibility of ultrathin absorber layer of CdS/CdTe solar cell. In the proposed cell the CdTe layer was reduced and found that 1 μm CdTe layer is enough for acceptable range of cell conversion efficiency. The viability of this ultra-thin CdTe absorber layer was examined, together with 0.1 μm PbTe back surface field (BSF) layer to reduce the barrier height in valence band and to minimize the recombination losses at the back contact of the CdS/CdTe cell. It was found that the proposed ultra-thin cells have conversion efficiency of 21.11% (Voc = 1.04 V, Jsc = 23.509 mA/cm 2 , FF = 0.863) without BSF and with 100 nm PbTe BSF conversion efficiency increased to 21.83% (Voc = 1.05 V, Jsc = 23.895 mA/cm 2 , FF = 0.87) with only 0.8 μm of CdTe layer. Moreover, the normalized efficiency of the proposed cells linearly decreased with the increasing operating temperature at the gradient of -0.4%/°C, which indicated better stability of the cells with and without BSF.

Design of high performance and ultra-thin CdTe solar cells with SnTe BSF from numerical analysis

“…In fact, the increase of Voc and FF both has the largest contribution to improve the efficiency of ultra-thin CdTe solar cell in this numerical analysis. These results of cell performances with the insertion of SnTe BSF layer are agreeable to the related published works [6,7]. In this research work, the CdTe solar cell conversion efficiency showed highest value of 22.61% (Jsc = 24.27 mA/cm 2 , FF = 0.876, Voc = 1.06 V) at 0.7 m of CdTe absorber layer with SnTe BSF layer.…”

“…6 that without BSF and with SnTe BSF layer, the normalized efficiency of the cells is linearly decreased with the increase of operating temperature at a temperature coefficient (TC) of -0.18%/°C and -0.16%/°C respectively. This TC indicates better stability of the cells with BSF at higher operating temperature, which are in good agreement with related published works [6,7]. Fig.6: Effects of operating temperature on normalized efficiency IV.…”

“…al [4], Cu 2 Te as discussed by Hossain et. al [5], PbTe as discussed by Matin and Dey [6], GeTe as discussed by Dey et. al [7] and ZnTe is the most common BSF material.…”

Back contacts materials used in thin film CdTe solar cells—A review

“…Lead telluride (PbTe) has been suggested as a back contact material in 1D simulation studies. 97 XPS has suggested a low VBO between PbTe and CdTe(111) surfaces. 98 It was expected that a two-dimensional electron gas can form at the PbTe/CdTe (111) interface, probably increasing recombination but no experimental solar cell results were available until the work of Swartz et al (2019).…”

Numerical Investigation of Graphene as a Back Surface Field Layer on the Performance of Cadmium Telluride Solar Cell

“…The main purpose of providing a BSF layer in the structure of solar cells is to reduce the barrier width in the valence band and to reduce the recombination losses at the back surface of the CdS/CdTe solar cell [ 7 , 8 , 9 ]. The main technical problems of CdS/CdTe solar cells are related to higher efficiency, less material usage, and stable back contact formation [ 10 , 11 ]. These problems should be addressed and numerically evaluated to discover the unseen potentiality of CdS/CdTe solar cells for higher cell performance [ 10 , 11 , 12 , 13 ].…”