Suer Zhou1,Yangwei Shi2,James Drysdale1,Joel Smith1,Margherita Teddei2,Jian Wang2,Akash Dasgupta1,Ashley Marshall1,David Ginger2,Henry Snaith1
University of Oxford1,University of Washington2
Suer Zhou1,Yangwei Shi2,James Drysdale1,Joel Smith1,Margherita Teddei2,Jian Wang2,Akash Dasgupta1,Ashley Marshall1,David Ginger2,Henry Snaith1
University of Oxford1,University of Washington2
Silicon/perovskite tandem solar cells are a promising direction for increasing the power output of solar cells past the Shockley-Queisser limit for single junctions. The ideal bandgap of perovskite on top of silicon is around 1.68-1.70eV, which can be achieved by mixed cation, mixed halide perovskites, such as FA<sub>0.75</sub>Cs<sub>0.25</sub>Pb(I<sub>0.8</sub>Br<sub>0.2</sub>)<sub>3</sub>. However, there are still many challenges for wider bandgap compositions, such as ion migration and phase segregation effects. Under constant laser illumination, these compositions undergo light-induced halide segregation, which will impact the long-term stability during operation.<br/><br/>To stabilize wide-bandgap mixed halide perovskites, we employ benzylamine as a bulk additive. By optimizing the amount of additive in the film, we significantly improved the PLQY and charge carrier lifetime. Compared to applying benzylamine as a surface treatment<sup>1,2</sup>, the bulk additive approach gave better reproducibility and higher overall device performance. Time-resolved PL and ToF-SIMS reveal that the benzylamine is mostly distributed near the top and bottom surfaces, forming lower dimensional phases. Benzylamine passivates both the grain boundary and surface defects while hindering ion migration. Furthermore, adding benzylamine does not introduce halides that could incorporate into the perovskite and change the bandgap, unlike the more common approach of adding ammonium halides. Perovskite thin films and devices with benzylamine have improved light and moisture stability, beneficial for perovskite/silicon tandem applications.<br/><br/>References<br/>(1) Zhou, Y.; Wang, F.; Cao, Y.; Wang, J.-P.; Fang, H.-H.; Loi, M. A.; Zhao, N.; Wong, C.-P. Benzylamine-Treated Wide-Bandgap Perovskite with High Thermal-Photostability and Photovoltaic Performance. <i>Advanced Energy Materials</i> <b>2017</b>, <i>7</i> (22), 1701048. https://doi.org/10.1002/aenm.201701048.<br/>(2) Wang, F.; Geng, W.; Zhou, Y.; Fang, H.-H.; Tong, C.-J.; Loi, M. A.; Liu, L.-M.; Zhao, N. Phenylalkylamine Passivation of Organolead Halide Perovskites Enabling High-Efficiency and Air-Stable Photovoltaic Cells. <i>Advanced Materials</i> <b>2016</b>, <i>28</i> (45), 9986–9992. https://doi.org/10.1002/adma.201603062.