Hybrid lead halide perovskite solar cells (PSCs) in tandem application with copper indium gallium diselenide (CIGS) solar cells represent one of the most promising all-thin-film technologies for next-generation photovoltaic devices. To minimize parasitic near-infrared (NIR) absorption losses in the electrodes, this work advances hydrogen-doped indium oxide (IO:H) and indium zinc oxide (IZO) electrodes for semitransparent perovskite solar cells. The total NIR absorptance (800–1300 nm) of the perovskite top cell is reduced to <7%, maximizing the bottom cell output current. Already taking first steps toward up-scaling, the perovskite active area is increased to match the CIGS active area of 0.5 cm2, and the R S is optimized by the implementation of a metal grid. The semitransparent perovskite solar cell reaches a power conversion efficiency of 15%. Combined with a CIGS bottom solar cell, a 4-terminal-tandem solar cell with 23% power conversion efficiency is demonstrated. We conduct detailed current loss analyses of the complete tandem devices to monitor and evaluate the improvements of this work.

In this study, Deep Level Transient Spectroscopy (DLTS) measurements have been performed on Cu(In,Ga)Se2 (CIGS) solar cells from an inline co-evaporation system. The focus of this investigation is directed on the effect of rubidium-fluoride (RbF)-post-deposition treatment (PDT) on the defects in the CIGS absorber layer. Different traps can be identified and their properties are calculated. Herein, different methods of evaluations have been used to verify the results. Specifically, one minority trap around 400 meV was found to show a significant reduction of the trap density due to the alkali treatment. In contrast, a majority trap at approximately 600 meV is unaffected.

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Despite the efficiencies above 20% achieved with (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells, further efficiency improvements are necessary. One possibility is the implementation of a postdeposition treatment (PDT) process. The aim of this study is therefore to investigate the effect of rubidium‐fluoride (RbF)‐PDT on the performance and physical properties of the ACIGS absorber. For this purpose, the RbF source temperature of the PDT process of ACIGS films with Ag/(Ag+Cu) (AAC) ratios of 5% from a multistage co‐evaporation inline process was systematically varied. It was shown that the efficiency of the devices is reduced by the PDT process, unlike observed for Cu(In,Ga)Se2 (CIGS) absorber, and is strongly influenced by the amount of rubidium. The behavior can be attributed to a strong reduction of the doping, which results from a changed doping mechanism. Furthermore, evidence for the formation of an additional layer was found. In addition, deep level transient spectroscopy (DLTS) measurements were performed on the samples showing a strong signal at low temperatures. This minority trap signal is strongly influenced by the amount of Rb and shows a systematically changing energetic position towards the middle of the band gap and an increasing density. Based on pulse variation measurements, the associated defect could be identified as an extended defect, indicating a location of the defect at grain boundaries.