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In two-terminal monolithic perovskite/silicon tandem solar cells, top and bottom cells are interconnected in series. To maximize the current of the entire tandem solar cell, current matching of the two sub-cells is needed. Thus, it is necessary to get access to the individual current of each sub-cell. As it is difficult to measure the absolute external quantum efficiency (EQE) for multijunction solar cells in general and especially if perovskite is involved, in this work, the spectrometric characterization technique enables important insight in the sub-cells' current limitation. In this method, which has already been applied for III-V multijunction solar cells, current-voltage curves are recorded while the spectrum is systematically varied from a blue-rich to a red-rich spectrum. We apply this technique to perovskite/silicon tandem devices consisting of a silicon heterojunction bottom solar cell and top solar cell in the p-i-n architecture with different perovskite absorbers. In our example, a perovskite absorber with a bandgap of 1.68 eV the top solar cell limits the current, whereas current matching could be reached when using an absorber with a lower bandgap of 1.64 eV. Results from spectrometric characterization are then used to scale the EQEs. We show how optimization strategies for both sub-cells can be systematically derived from these results. [ABSTRACT FROM AUTHOR]

Using hot-wire chemical vapor deposition (HWCVD), an attractive alternative to the established plasma-enhanced chemical vapor deposition (PECVD), we aim to deposit silicon films for silicon heterojunction (SHJ) solar cell applications. Because of the absence of energetic particles in HWCVD, the layers grow softly and free of damage, hence promising excellent surface passivation and therefore highly efficient solar cells. We report the investigation of intrinsic silicon films, acting as passivation layers, by adjustment of the deposition parameters, with a focus on the substrate temperature as the most important factor. Passivation layers, prepared with differing deposition parameters, were characterized by measurement of the minority-carrier lifetimes using the photoconductance method. At 6 nm a-Si:H thickness, average minority-carrier lifetimes of 1.2 ms were obtained on textured substrates. By combining the optimized HWCVD passivation films and doped silicon films deposited by PECVD, cell efficiencies of 19.7% were achieved. By also depositing the n- und p-doped a-Si:H films by HWCVD cell efficiencies above 18.2% were obtained on a 145 x 145 mm² cell area. [ABSTRACT FROM AUTHOR]