K3Ti2Cl9−xBrx: structurally stable lead-free perovskites as permissive absorbers for solar cell and visible-light photocatalysis

Abstract

The toxicity issues with lead-based perovskite solar cells sparked interest in lead-free alternatives, such as K₃Ti₂Cl_9−xBr_x (x = 0, 3, 6, and 9), which are environmentally friendly. The optical, structural, and electrical properties of K₃Ti₂Cl_9−xBr_x (x = 0, 3, 6, and 9) are investigated using density-functional theory in this study to assess their potential as absorber materials for solar cells. Phonon dispersion is used to determine the dynamical stability of these perovskites in addition to their formation energy, which further provides evidence regarding their stability. The TB-mBJ indicates its direct bandgap along the M–M direction and indirect bandgap at the M–K direction and lie within the ideal range for photoelectric conversion. The SCAPS-1D program is employed to identify the optimal solar cell designs that integrate various ETLs and HTLs. The structure with the highest power conversion efficiency out of the fifty four configurations examined is FTO/WS₂/K₃Ti₂Cl_9−xBr_x (x = 0, 3, 6 and 9)/CuI, provides the highest performance with an efficiency of 19.11, 24.68, 25.25 and 29.00%, FF of 82.14, 81.53, 80.09 and 62.07%, V_oc of 1.30, 1.29, 1.25 and 1.35 V and J_sc of 17.84, 23.42, 25.88 and 27.00 mA cm⁻² with the addition of recombination effect. Additionally, the effect of thickness, defect density, series and shunt resistance is also examined. Photocatalytic analysis shows that all of these compounds are capable of converting H₂O to O₂ and H₂. In the same way that the compounds under study may reduce N₂ to NH₃, they can likewise reduce CO₂ to CH₄OH and CH₄. In comparison to other materials, these compounds have an effective efficiency for reducing CO₂ and N₂ and their photocatalytic efficiency for water splitting is higher than the intended value for industrial applications. Future research should focus on developing lead-free, totally inorganic perovskite photovoltaics and photocatalysts with enhanced photovoltaic and photocatalytic performance. Such materials could have uses in photocatalysis, especially in visible light-driven processes like water splitting, CO₂ reduction, and N₂ fixation and are highly promising for use in photovoltaics and high-performance optoelectronics because they all have absorbers with strong visible-light absorption, a large PCE, and a high quantum efficiency.