Research into 2D layered hybrid perovskites is on the rise due to the enhanced stability of these materials compared to 3D hybrid perovskites. Recently, interest towards the use of functional organic cations for these materials is increasing. However, a vast amount of the parameter space remains unexplored in multi-layered (n > 1) hybrid perovskites for solar cell applications. Here, we incorporate carbazole derivatives as a proof of concept towards the use of tailored functional molecules in multi-layered perovskites. Films of low-n carbazole containing perovskites show high photoconductivity half-lifetimes. Higher-n (〈n〉 = 40) multi-layered perovskite films possess charge carrier diffusion lengths comparable to MAPI thin films. Solar cells containing these materials have comparable efficiencies to our MAPI and phenethylammonium (PEA)-containing multi-layered perovskite reference devices. Moisture stability tests were performed both at the material and device levels. In comparison to MAPI and PEA-based materials and solar cells, the addition of a small percentage of the carbazole derivative to the perovskite material significantly enhances the moisture stability.

The perovskite solar cell is considered a promising candidate as the top cell for high-efficiency tandem devices with crystalline silicon (c-Si) bottom cells, contributing to the cost reduction of photovoltaic energy. In this contribution, a simulation method, involving optical and electrical modelling, is established to calculate the performance of 4-terminal (4T) perovskite/c-Si tandem devices on a mini-module level. Optical and electrical characterization of perovskite and c-Si solar cells are carried out to verify the simulation parameters. With our method, the influence of transparent conductive oxide (TCO) layer thickness of perovskite top cells on the performance of tandem mini-modules is investigated in case of both tin-doped indium oxide (ITO) and hydrogen-doped indium oxide (IO:H). The investigation shows that optimization of TCO layer thickness and replacement of conventional ITO with highly transparent IO:H can lead to an absolute efficiency increase of about 1%. Finally, a practical assessment of the efficiency potential for the 4T perovskite/c-Si tandem mini-module is carried out, indicating that with a relatively simple 4T tandem module structure the efficiency of a single-junction c-Si mini-module (19.3%) can be improved by absolute 4.5%.