At the top of the stack is a contact side of the top GaAs cell is only 4μm thick and is transparent to infrared light. Its efficiency is 23.4% which is close to the effectiveness of standard GaAs cells. IMEC has succeeded in transferring this cell of GaAs in a top to bottom Ge cell, creating a mechanical stack. In that pile, Ge bottom cell is contacted separately. It has a potential efficacy of 3-3.5%, which is higher than Ge bottom cells in the state of the art monolithically stacked InGaP / (In) GaAs / Ge cells. Looking ahead, Giovanni Flamand, team manager at IMEC, a job expected to show first triple-junction cells from 2010.

This cell is an innovative technology demonstrator IMEC to produce mechanically stacked, high-efficiency InGaP / GaAs / Ge triple-junction solar cells. This includes world-class manufacturing thin-film III-V and the cells Ge bottom cells and the development of mechanical technology stack them. The conversion efficiency is expected 1-2% higher than those obtained today join in monolithic triple solar cells (> 40% concentrated illumination). In addition, new cells show enhanced spectral robustness. Stacked solar cells combine cells of different materials to capture and converse more of the light spectrum than is possible with a single material.

Dr. Jef Poortmans, photovoltaic IMEC Program Director: “mechanical batteries are more complex to manage and interconnect. But surely offer a way to increase conversion efficiency and high efficiency energy performance of solar cells. And enable an effective way to try new combinations of materials. For this technology, we benefit from the experience of 3D stacking IMEC increasingly layers III-V, and processing of solar cells. ”

Source: IMEC