Unlocking the potential of metal halide perovskite thermoelectrics through electrical doping: A critical review

Over the past decade, metal halide perovskites (MHPs) have received great attention, triggered by the tremendous success of their record-breaking power conversion efficiency values in solar cells. Recently, there have been significant interests in fully utilizing their unique properties by exploring other device applications including thermoelectrics, which is promising due to their ultralow thermal conductivity and high mobility relative to their competitors among solution-processable materials. However, the performance of MHP thermoelectrics reported so far falls significantly short of theoretical predictions, as the doping levels achieved to date are typically below the optimum values for maximizing the thermoelectric power factor, indicating the need for effective electrical doping strategies. In this critical review, recent studies aimed at enhancing the thermoelectric properties of MHPs are discussed, with a focus on the relatively under-explored area of electrical doping in MHPs. The underlying charge transport mechanism and doping effect on transport are also examined. Finally, the challenges facing MHP thermoelectrics are highlighted, and potential research visions for achieving highly efficient thermoelectric conversion based on MHPs are offered.