Exploring the Optoelectronic and Photovoltaic Characteristics of Lead-Free Cs2TiBr6 Double Perovskite Solar Cells: A DFT and SCAPS-1D Investigations

Abstract

In recent times, the remarkable advancements achieved in the field of perovskite solar cells (PSCs) have sparked significant research efforts aimed at enhancing their overall performance because of their exceptional optoelectronic properties. Due to the toxicity of lead (Pb), the emergence of Ti-based (Cs₂TiBr₆) double-halide PSCs is regarded as a good alternative to Pb-based PSCs. Here, density functional theory (DFT) calculations are performed to examine the prospect of Cs₂TiBr₆ perovskite as a layer of absorber for photovoltaic cells (SCs). These computations looked at the material's structural, optical, and electrical characteristics. The density of states (DOS) results demonstrate strong conductivity, principally provided by the 4p states of Br, whilst Ti-3d and Cs-5p orbital electrons offer insignificant contributions. The electronic band structure discloses a direct band gap of 1.534 eV. The covalent connections that exist between Ti and Br atoms and the robust electronic charge density around the Ti atom both demonstrate a significant buildup of electronic charge along the 100 planes. The dielectric function and the coefficient of absorption have significance irrespective of lower energies because it is extremely valuable for solar energy applications. The UV absorption peaks of Cs₂TiBr₆ have a maximum of ≈15.51 eV and are magnified with photon energy up to 2.46 eV, indicating that it may have potential for solar applications. This work also investigated a good combination of the hole transport layer (HTL) and electron transport layer (ETL) with the Cs₂TiBr₆ absorber layer. AZnO, Nb₂O₅, LBSO, and Zn₂SnO₄ are executed as the ETLs, and MoO₃, CuAlO₂, MEH-PPV, ZnTe, CNTS, GaAs, MoS₂, PTAA, Cu₂Te, Zn₃P₂ are considered as the HTLs to identify the best HTL/Cs₂TiBr₆/ETL combinations using the SCAPS-1D numerical simulation. Among all configurations, ITO/LBSO/Cs₂TiBr₆/CNTS/Au is examined as the best-optimized structure of Ti-based PSC, with J_SC of 26.63 mA cm⁻², a V_OC of 1.123 V, FF of 82.94%, and a power conversion efficiency of 24.82%. To validate the findings, PV parameters like the effect of generation rate, recombination rate, J−V, and Q-E characteristics are evaluated. The effect of series and shunt resistance and structure working temperature are explored to observe the effect of these on PSC devices. The accomplished outcomes suggest that Cs₂TiBr₆ can be viewed as an optimistic material for PSCs for its higher stability and environment-friendly characteristics.