In addition to the broadly anticipated use of metal halide perovskites in photovoltaics and light-emitting devices, they also hold a great promise as cost-effective thermoelectrics, as they may offer an ultra-low thermal conductivity combined with a high Seebeck coefficient. This Review summarizes the recent advances in theoretical analysis and experimental studies of the thermoelectric properties of these materials, with a particular focus on organic–inorganic (hybrid) halide perovskites and low-dimensional analogues. After a short introduction of figures of merits of thermoelectric materials, we consider measurement methods used to characterize thermoelectric materials and outline some difficulties in applying those methods to perovskites, since accurate measurements are essential for further progress of this emerging research area. We then outline in detail the current progress achieved in metal halide perovskite thermoelectrics and offer a detailed discussion of possible strategies to resolve the discrepancy between their high theoretically predicted ZT values (1–2 at room temperature) and still rather low (below 0.2) experimental values.

Photoinduced halide segregation (PHS) is a process of critical importance for the performance of perovskite solar cells with mixed halide absorber layers. However, PHS is still not well understood, especially in the case of layered mixed halide perovskites (MHPs), which are less commonly studied compared to their 3D counterparts. Here, we investigated temperature-and light-induced PHS in 2D MHPs with a phenylpropylammonium (PPA) spacer. We found that 2D PPAbased MHPs exhibited complex segregation behavior dependence on temperature and illumination intensity with the suppression of segregation observed at high temperature (attributed to the highly exothermic nature of the process) as well as moderate illumination intensities, illustrating the importance of additional processes present in this particular material, which exhibits distinctly different behavior compared to 2D MHPs with other aromatic cations.

We investigated the influence of two passivating molecules containing a P�O group on the performance of quasi-2D Dion−Jacobson halide perovskite light-emitting diodes, namely, triphenylphosphine oxide (TPPO) and diphenyl-4triphenylsilylphenyl phosphine oxide (TSPO1). We found that both passivating molecules lead to increased efficiency compared to control devices, while they had opposite effects on device lifetime, with a decrease observed for TPPO and an increase observed for TSPO1. The two passivating molecules resulted in differences in energy-level alignment, electron injection, film morphology and crystallinity, and ion migration during operation. While TPPO resulted in improved photoluminescence decay times, overall higher maximum external quantum efficiency (EQE) and device lifetime were obtained for TSPO1 compared to TPPO (14.4% vs 12.4% EQE, 341 min vs 42 min T 50 ).