<p>The structural, electrical optical properties and solar cell efficiency of halide perovskite Cs₂TlBiZ₆ (Z = Cl, Br and I) are investigated using DFT through WEIN2k and SCAPS-1D tools. The reported findings of structural properties are closely align with the experiments. The electronic properties of Cs₂TlBiZ₆ (Z = Cl, Br and I) reveal the direct BG semiconductor and are dynamic in the visible light spectrum. The results demonstrate that the BG is reduced when Cl is replaced by Br and I respectively. The optical characteristic investigations revealed that these compounds are appropriate for optoelectronic and solar cell devices due to their dynamic visible-range optical characteristics. To model the efficiency of these perovskites based solar cells, Ws₂ is taken as the electron transport layer (ETL), CBTS as the hole transport layer (HTL), and Cs₂TlBiZ₆ (Z = Cl, Br and I) as the absorber layer. Among the three the most effective solar cells is the FTO/Ws₂/Cs₂TlBiI₆/CBTS/Cu compared with the other two (FTO/Ws₂/Cs₂TlBiI₆ (Z = Cl, Br) /CBTS/Cu). The solar cell parameters of all the devices are J_SC of 16.85, 17.10 and 17.69&#xa0;mA/cm², V_OC of 1.24, 1.26 and 1.24&#xa0;V, FF of 71.93, 73.43 and 81.77% and PCE of 17.64, 15.94 and 17.95% respectively. Therefore, subsequent studies may develop lead-halide free, inorganic perovskite photovoltaics that perform better, according to our research.</p>