Alkali bismuth dichalcogenides of the general formula ABiE2 (A = Li+, Na+, K+, Rb+; E = S2-, Se2-, Te2-) are predicted to have properties beneficial to both photovoltaics and thermoelectrics, but they have only been scarcely investigated for either application. RbBiS2 is predicted to have both a 1.1 eV indirect and 1.5 eV direct band gap, a high dielectric constant of 37.94, and low effective mass of electrons of 0.2 all of which are beneficial for photovoltaics. Compositions composed of A = Li+, Na+, K+ and E = S2-, Se2-, Te2- have a rock salt structure containing mixed A+:Bi3+ sites that cause the unit cell to have a high degree of disorder that should lead to a lower lattice thermal conductivity. This effect in combination with nanostructuring and the formation of solid solutions further increases the thermoelectric figure of merit in these materials. Herein, we explore the nanoscale synthetic flexibility of this system and we investigate the effects of the various possible cation site occupancies on the electronic band structure.

Alkali bismuth dichalcogenides: Emerging energy materials for photovoltaics and thermoelectrics

253rd National Meeting (2017)

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