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Perovskite–silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite–silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. We show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. Our optically advanced rear reflector with a dielectric buffer layer results in reduced parasitic absorption at near-infrared wavelengths. As a result, we demonstrate a certified power conversion efficiency of 29.80%.Designing gentle sinusoidal nanotextures enables the realization of high-efficiency perovskite–silicon solar cells

Silicon-perovskite tandem solar cells have remarkable power conversion efficiencies (PCEs) and can contribute to the rapid transition towards renewable energy sources. While inorganic perovskite solar cells show superior temperature stability as compared to organic-inorganic perovskite solar cells, they have lower PCEs and lower open-circuit voltages (VOC), i.e. a higher voltage loss. In addition, a strong hysteresis in current density-voltage measurements is common and results in a reduced stabilized power output. This thesis investigates the reasons for this and presents solutions for the higher voltage loss and hysteresis in inorganic perovskite solar cells. By conducting intensity-dependent photoluminescence (PL) measurements on perovskite layers with and without each charge-selective transport layer (CTL), the contribution of each interface to the voltage loss could be quantified. This allowed for a targeted improvement of the limiting interface. For p-i-n CsPbI2Br perovskite solar cells, a lithium fluoride interlayer between the perovskite and the CTL C60improved the energy level alignment and decreased the defect density at the interface. Even though the VOC was improved by 110 mV, a strong mismatch between quasi-Fermi level splitting (QFLS) and VOC remained. The perovskite/C60 interface was also found to limit the efficiency of p-i-n DMAI-CsPbI3 perovskite solar cells. A surface treatment of the perovskite layer using 1,4-butanediamine (DAB) improved this interface, removing the QFLS−e· VOC mismatch. In combination with a passivation layer consisting of the fluorinated sodium molecule F-Na, the limitation of the perovskite/C60interface could be overcome, and the VOC and fll factor could be substantially increased. These targeted improvements resulted in p-i-n DMAICsPbI3 perovskite solar cells with a PCE of 20.05 %. A comparative loss analysis showed that the voltage loss is almost as low as in state-of-the-art triple-cation perovskite solar cells, but the perovskite/C60interface needs further improvement. Measurements on CsPbI2Br and DMAI-CsPbI3 perovskite solar cells revealed one order of magnitude higher ion densities and one to two orders of magnitude lower mobilities than in organic-inorganic perovskite solar cells. Mobile ions were found to decrease the PCE, most likely by accumulating at the interfaces, screening the internal field and therefore increasing non-radiative recombination. Even though the ion densities were similar, this decrease in PCE was lower in DMAI-CsPbI3m perovskite solar cells as compared to CsPbI2Br perovskite solar cells. This suggests that the more effective interface passivation in DMAI-CsPbI3 perovskite solar cells can decrease the non-radiative recombination at the interface even at high ion densities, resulting in a lower hysteresis. These results addressed the main challenges for inorganic perovskite solar cells and presented new potential top cells for silicon-perovskite tandem solar cells.