Haertel, M.; Li, B.; Mariotti, S.; Wagner, P.; Ruske, F.; Albrecht, S.; Szyszka, B.: Minimizing sputter damage-induced electrical losses in monolithic perovskite/silicon tandem solar cells during deposition of the transparent front-electrode. In: 2023 IEEE 50th Photovoltaic Specialists Conference (PVSC), San Juan, PR, USAPiscataway, NJ: IEEE, 2023. - ISBN 978-1-6654-6059-0, p. 1
10.1109/pvsc48320.2023.10359891
Abstract:
The front electrode of monolithically integrated perovskite/silicon tandem solar cells commonly consists of a transparent conductive oxide (TCO). TCOs are usually deposited using the well-established method of magnetron sputtering. High particle energies, however, can cause sputter damage to sensitive substrates during the deposition process. Therefore, a SnO2 buffer layer is used in all current perovskite top-cell designs with p-i-n polarity and competitive efficiencies. Here, we propose a methodology to identify electrical losses in perovskite solar cells (PSC) caused by sputter damage during the TCO deposition. We also show a simple method for minimizing sputter damage to the PSC, which enables SnO2 buffer layer-free devices. Evaluation of the ideality factor and pseudo-current density-voltage (J-V) curves, reconstructed from light intensity-dependent J-V measurements on tandem top-cell-equivalent semi-transparent single-junction PSCs, revealed that sputter damage causes transport and non-radiative recombination losses. These losses result in a lower open-circuit voltage (VOC) and fill factor (FF), limiting the PSC performance. By lowering the sputter power density, we reduced the impact of sputter damage. This resulted in improved VOCs (~13 m V) and FFs (-3%) of the semi-transparent PSCs, which is a direct consequence of the reduced electrical losses [1]. Finally, we applied our low-damage sputter approach on SnO2 buffer layer-free monolithic perovskite/silicon tandem devices. Compared to tandem devices with a SnO2 buffer layer, the SnO2 buffer layer-free devices were optically superior, resulting in a device current density improvement of 0.52 mA/cm2 due to increased current densities in both sub-cells. This is an important development for further optical performance optimization of tandem devices.