Theoretical investigations of electronic and optical properties of double perovskite Cs$_2$Tl$BX_6$ ($B=$ Bi, In; $X=$ Cl, Br, I) for photovoltaic application

Ardimas; Edi Suprayoga

doi:10.1016/j.mtcomm.2025.112690

paper

Theoretical investigations of electronic and optical properties of double perovskite Cs $_{2}$ Tl $B X_{6}$ ( $B =$ Bi, In; $X =$ Cl, Br, I) for photovoltaic application

arXiv:2505.09982 · doi:10.1016/j.mtcomm.2025.112690

Abstract

Lead-free double perovskites are gaining attention for photovoltaic (PV) applications due to their long carrier lifetimes, tunable bandgaps, and low toxicity. Using first-principles calculations, we studied the structural, electronic and optical properties of Cs $_{2}$ Tl $B X_{6}$ ( $B =$ Bi, In; $X =$ Cl, Br, I). The cubic phase (space group Fm3m) was analyzed within the projector-augmented wave (PAW) method. Our calculations predict direct bandgaps of 1.9-1.2 eV for Cs $_{2}$ TlBi $X_{6}$ and indirect bandgaps of 2.4--0.8 eV for Cs $_{2}$ TlIn $X_{6}$ . Notably, the bandgap energy decreases with anion substitution from Cl to I, making these materials highly active in the near-infrared to visible light range. We reveal that Cs $_{2}$ TlBi $X_{6}$ exhibits the highest optical absorption, with a peak value of $5 \times 1 0^{5}$ cm $^{- 1}$ at an incident photon energy of 3 eV. Additionally, we evaluated the transport properties using the Boltzmann transport equations. The results indicate that Cs $_{2}$ TlBi $X_{6}$ exhibit high electrical conductivity, reaching $8 \times 1 0^{6}$ S/m, and high electron mobility of 120 cm $^{2} /$ V.s. PV performance analysis further reveals promising power conversion efficiencies (PCE) of up to 42\%, with Cs $_{2}$ TlBi $X_{6}$ showing significantly higher PCE than Cs $_{2}$ TlIn $X_{6}$ . These reports highlight the potential of Cs $_{2}$ TlBi $X_{6}$ for advanced photovoltaic devices.

13 pages, 9 figures

Theoretical investigations of electronic and optical properties of double perovskite Cs2​TlBX6​ (B= Bi, In; X= Cl, Br, I) for photovoltaic application

Abstract

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Theoretical investigations of electronic and optical properties of double perovskite Cs $_{2}$ Tl $B X_{6}$ ( $B =$ Bi, In; $X =$ Cl, Br, I) for photovoltaic application