Design of CuIn 1− y Ga y Se 2 /Si 1 − x Ge x Tandem solar cells with controlled current matching

Abstract

A tandem solar cell including of CuIn1−yGaySe2/Si1 − xGex was exhibited by integrating a CuIn1−yGaySe2 solar cell on a Si1 − xGex solar cell to achieve a conversion efficiency of about 26% by controlled current matching. Electrical analyses were used to determine the performance parameters of the bottom and top sub-cells. In this work, an experimental Si0.73Ge0.27 solar cell has been modelled. The photovoltaic characteristics of the Si0.73Ge0.27 solar cell are in good agreement with its experimental counterpart. Afterwards, a copper–gallium–diselenide (CGS)/Si0.73Ge0.27 tandem solar cell with 24.1% efficiency has been designed. Additionally, the bandgap combination of CuIn1−yGaySe/Si1 − xGex structure has been studied. The findings indicate that CuIn1−yGaySe/Si1 − xGex tandem cell with 0.7 < y< 1 and 0 < x< 0.7 can achieve acceptable efficiency and the optimised CGS/Si device with 26.1% efficiency is proposed. In CGS/Si0.73Ge0.27 tandem cell, the current matching is obtained when the CGS thickness of the top cell is 1 µm and the Si0.73Ge0.27 absorber thickness of the bottom cell is 1.9 µm. The current matching condition for this device degrades the fill factor, although increases the current, so the device does not achieve maximum output power.