Er-raji, O.; Mahmoud, M.A.A.; Fischer, O.; Ramadan, A. J.; Bogachuk, D.; Reinholdt, A.; Schmitt, A.; Kore, B.P.; Gries, T.W.; Musiienko, A.; Schultz-Wittmann, O.; Bivour, M.; Hermle, M.; Schubert, M.C.; Borchert, J.; Glunz, S.W.; Schulze, P.S.C.: Tailoring perovskite crystallization and interfacial passivation in efficient, fully textured perovskite silicon tandem solar cells. Joule 8 (2024), p. 2811-2833
10.1016/j.joule.2024.06.018
Open Access Version
Abstract:
Context & scale Fully textured perovskite silicon tandem solar cells rely on the deposition of the perovskite absorber on textured silicon with a >1 μm pyramid size, which represents the current standard in the industry. To bridge the gap between research and industry, these cells must demonstrate a high power output. Nevertheless, perovskite absorbers deposited on large pyramids often suffer from a high grain boundary defect density and poor interfacial passivation at the perovskite/electron transport layer (C60) junction. We tackle both loss mechanisms by introducing a multi-functional additive (urea), which simultaneously regulates the perovskite crystallization as well as passivates the perovskite/C60 interface. Moreover, this strategy is employed at a low annealing temperature (100°C, different from the standardly used 150°C), thus enabling an effective lowering of the perovskite annealing’s thermal budget. This approach is of high relevance for the industrialization of perovskite silicon tandem solar cells. Summary Fully textured perovskite silicon tandem solar cells are promising for future low-cost photovoltaic deployment. However, the fill factor and open-circuit voltage of these devices are currently limited by the high density of defects at grain boundaries and at interfaces with charge transport layers. To address this, we devise a strategy to simultaneously enhance perovskite crystallization and passivate the perovskite/C60 interface. By incorporating urea (CO(NH2)2) as an additive in the solution step of the hybrid evaporation/spin-coating perovskite deposition method, the crystallization kinetics are accelerated, leading to the formation of the desired photoactive phase at room temperature. With that, perovskite films with large grain sizes (>1 μm) and improved optoelectronic quality are formed at low annealing temperatures (100°C). Concurrently, remnant urea molecules are expelled at the perovskite surface, which locally displaces the C60 layer, thus reducing interfacial non-radiative recombination losses. With this strategy, the resulting tandem solar cells achieve 30.0% power conversion efficiency.