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

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 ultra-thin 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.