Copper telluride as a nobel BSF material for high performance ultra thin CdTe PV cell

Thin-film CdTe is one of the leading materials for high efficiency, low-cost and stable PV cells. The formation of a stable, low resistance, non-rectifying back contact to p-CdTe thin-film is the most critical challenge associated with this technology, another main constraint of PV technology is its high cost. To reduce the cost, less material consumption is desirable. Thus research is leading toward ultra-thin CdTe PV cell. However, the use of back surface field (BSF) material is found to be better, effective and easier one among several methods still used to overcome the problem with the back contact. This paper numerically explores the possibility of high efficiency, ultra-thin and stable CdTe cells with Cu₂Te BSF. The cell performances (Voc, Jsc, FF, efficiency, temperature stability) are investigated by recognized simulator `Analysis of Micro-electronics and Photonic Structures´ (AMPS-1D). A modified structure of CdTe based PV cell SnO₂/Zn₂SnO₄/CdS/CdTe/Cu₂Te/Ni has been proposed over reference structure SnO₂/ Zn₂SnO₄/CdS/CdTe/Cu. The simulated results have shown that the use of Cu₂Te as BSF layer enhances the cell performances and has no adverse effect on cell stability. In this analysis the highest conversion efficiency of CdTe based PV cell without BSF has been found around 17% using CdTe absorber thickness of 5μm, on the other hand with the BSF the conversion efficiency has been found to be as high as 19.5% using only 0.6 μm thick CdTe absorber, which opens a new window for ultra-thin CdTe PV cells. Furthermore it was also found that the cell normalized efficiency linearly decreased with the increasing operating temperature at the gradient of -0.35%/C, which indicates better stability of the proposed CdTe PV cell.