Research Projects

Thermoelectricity, an efficient technology for the direct conversion of heat into electricity (and vice versa), has attracted intense scientific attention in recent years, particularly in the area of re-harvesting the waste heat to recompense the demand for eco-friendly, alternative energy. The efficiency of a thermoelectric (TE) material is described by the dimensionless figure of merit, ZT = α²σT/κ where α, σ, κ, and T is the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively. A good TE material should have a high Seebeck coefficient for the maximum conversion of heat to electricity or electricity to cooling/heating, high electrical conductivity to minimize Joule heating, and low thermal conductivity to prevent thermal shorting. Though TE technology is being used in space crafts and high-end automobiles, the exiting state-of-the-art TE materials (Bi₂Te₃, PbTe, Cu₂Se, etc.) are expensive, heavy, brittle, and have limited suitability for large-area applications such as waste heat harvesting. The high fabrication and material cost of existing TE material has motivated us to think about alternative materials with simple, low-cost, and reliable solution-based fabrication processes. In this context, halide perovskites (HPs) have recently attracted significant attention as a potential TE material because of their high Seebeck coefficient and low thermal conductivity. Accordingly, these materials are classified as “phonon glass, electron crystal”, where the charge transport is as efficient as in conventional semiconductors, and heat transport is hindered as in a glass. Theoretical studies have predicted that the TE performance of HPs is comparable with traditional, high-efficiency bulk TE materials such as Bi₂Te₃. However, HPs have a low carrier concentration, low electrical conductivity, and lack of stability which impedes widespread application. Several strategies are being used to address these drawbacks in recent years, particularly, through various doping strategies and utilizing two-dimensional (2D) layered perovskite. In this project, we propose to develop 2D, stable halide perovskite-based TE materials for efficient waste heat harvesting and conversion to electricity. We wish to employ all inorganic 2D Ruddlesden-Popper (RP) layered perovskites instead of the conventional 3D perovskites. RP perovskites have emerged as one of the most promising HP materials because of their potential for combining high performance with long-term stability, which has been a long-standing issue in the field of HPs. For the RP perovskite, the availability of layers within the base unit helps in the tunability in their optoelectronic properties and simultaneously improves their stability. Doping at different sites is also proposed here for high-efficiency TE devices with excellent long-term stability and reliable device operations.

Thermoelectric materials, 2D Perovskites, Photophysical properties, Waste heat conversion