Thin film solar cell efficiency enhancement using a gradient doping absorbent layer

In this contribution, we propose a numeric exploration of a copper indium gallium diselenide (CIGS) based thin film solar cell structure by means of SILVACO's technology computer aided design (T-CAD). We found the performance of our proposed cell and that of experimental champion very similar. High resistance and surface recombination near the rear contact alongside with bulk recombination reduce solar cell performance. In order to get a cell performance enhancement, we suggest the introduction of an additional electric field via gradient doping in absorbent layer in order to reduce the latter phenomenon effects. Therefore, both graded and uniform doping profiles have been studied then compared. Our results demonstrated that the graded doping in CIGS absorbent layer gives higher conversion efficiency (η) than uniform one. Structure with 0.11, 0.04, 0.01, and 2 μm thicknesses of MgF2, n-ZnO, n-CdS, and p-CIGS layers, respectively, gives the best performance. A graded doping of (3 × 1016-1022) cm−3 concentration in CIGS layer, 1022 cm−3 in ZnO layer, and 1021 cm−3 in CdS layer give a conversion efficiency of 29.43% in comparison to 22.92% of the proposed cell at room temperature.