Although the fundamental limits have been established for the single junction solar cells, tandem configurations are one of the promising approaches to surpass these limits. One of the candidates for the top cell absorber is CdTe, as the CdTe photovoltaic technology has significant advantages: stability, high performance, and relatively inexpensive. In addition, it is possible to tune the CdTe bandgap by introducing, for example, Zn into the composition, forming Cd_1−xZn_xTe alloys, which can fulfill the Shockley–Queisser limit design criteria for tandem devices. The interdigitated back contact (IBC) silicon solar cells presented record high efficiencies recently, making them an attractive candidate for the rear cell. In this work, we present a combined optical and electrical optimization of Cd_1−xZn_xTe/IBC Si tandem configurations. Optical and electrical loss mechanisms are addressed, and individual layers are optimized. Alternative electron transport layers and transparent conductive electrodes are discussed for maximizing the top cell and tandem efficiency.

Organic–inorganic hybrid perovskite materials are excellent candidates as light absorbers in tandem solar cells with advantages of tunable bandgaps, high absorption coefficients, and facile and low-cost fabrication processes. As the key component of a tandem structure, the interconnecting layer (ICL) requires optical transparency, efficient carrier recombination, and facile up-scalability. To demonstrate the feasibility of an efficient TCO-free ICL in all-perovskite tandem solar cell devices, we have performed a comprehensive computational analysis using the transfer matrix method. The results suggest that varying the silver recombination layers up to 3 nm does not present a significant effect on the maximum achievable photocurrent (MAPC) of the cell. Moreover, the highest MAPC from the tandem cell with the lowest sensitivity to electron and hole transport layer thicknesses can be obtained by the transport layers with refractive indices within the range of 1.9–2.6. The findings are of direct practical relevance, i.e., with meeting our optical framework, a fabrication procedure can be merely directed toward the electrical optimization of the ICL. The presented methodology can serve as an introduction to benchmark ICL design for multi-junction excitonic solar cells.