Project R-13655

ENGAGED – The effect of ion migration on the long-term stability of tandem solar cells and the tunnel junction (Research)

With the maturing of thin film single junction solar cell technology, the next step to reach even higher efficiencies is to apply these solar cells in a tandem structure. One of the interesting combinations recently investigated are perovskite on chalcogenide tandems, with over 24% solar cell efficiency already achieved. Crucial for real life application is their long-term stability. Thin film solar cells have inherited instability issues due to the thin layer deposition and the many interfaces. Most of these instabilities are being reduced by interface engineering. When the thin films are applied into a monolithic tandem solar cell, additional intermediate layers are used to electrically connect both cells. These intermediate layers are thus added to the full stack, and how they are performing over longer time is not yet known. In this proposal, we want to investigate the stability of the full tandem stack, with a focus on the intermediate layers. The separate solar cells are known to suffer instability issues due to mobile ions. These ions will also diffuse to the intermediate layers and hypothetically modify their properties over time. Using advanced opto-electronical characterization and modelling in combination quantification of the mobile ions diffusion into the tunnel junction we aim to unravel prospective stability issues in the complete tandem solar cell. Based on the results, more stable designs based on interface engineering will be proposed.

01 January 2023 - 31 December 2026