Minimizing Open‐Circuit Voltage Losses in Perovskite/Perovskite/Silicon Triple‐Junction Solar Cell with Optimized Top Cell
Minasadat Heydarian, Minasadat Heydarian, Athira Shaji, Oliver Fischer, Michael Günthel, Orestis Karalis, Maryamsadat Heydarian, Maryamsadat Heydarian, Alexander J. Bett, Hannes Hempel, Martin Bivour, Florian Schindler, Martin C. Schubert, Andreas W. Bett, Stefan W. Glunz, Juliane Borchert, Patricia S. C. Schulze
Abstract
Following the impressive efficiencies achieved for two‐terminal perovskite/silicon dual–junction solar cells, perovskite/perovskite/silicon triple‐junction cells have now gained attention and are rapidly developing. In a two‐terminal triple‐junction cell, maximizing the open‐circuit voltage ( V OC ) is not straightforward as it requires understanding and mitigating the dominant losses in such a complex structure. Herein, the high bandgap perovskite top cell is first identified as the main source of the V OC loss in the triple‐junction cell. A multifaceted optimization approach is then implemented that improves the V OC of the 1.83 eV perovskite. This approach consists of 1) replacing the reference triple‐cation/double‐halide with a triple‐cation/triple‐halide perovskite, which improves perovskite bulk quality and reduces transport losses, and 2) implementing a piperazinium iodide passivation between the perovskite and the electron transport layer, which reduces nonradiative recombination losses at this interface. Employing these optimizations in the top cell of the triple‐junction boost the V OC by average 124 mV. A high V OC of more than 3.00 V is achieved with a fill factor of 79.6%, a short‐circuit current density of 9.0 mA cm −2 , and an efficiency of 21.5%. Further study is conducted on the improvement of V OC in the triple‐junction solar cell using subcell selective photoluminescence‐based implied V OC imaging, which is applied for the first time to a perovskite‐based triple‐junction structure.