Ti-based Cs?TiBr? double-halide perovskites are promising for optoelectronic and renewable energy applications, offering a non-toxic alternative to Pb-based perovskite solar cells (PSCs). This study uses SCAPS-1D to simulate a Cs?TiBr?-based PSC incorporating a CZTS/NiO double hole transport layer (HTL) to enhance power conversion efficiency (PCE). The double HTL improves hole transport, strengthens electron blocking, and reduces interfacial recombination. The optimized FTO/CeOx/Cs?TiBr?/CZTS/NiO/Au architecture achieves a PCE of 27.78%, significantly higher than the prototype (11.62%), under optimized parameters including absorber and interface defect densities, electron capture cross-section, and CZTS thickness. Notably, the ETL-free structure (FTO/Cs?TiBr?/CZTS/NiO/Au) attains the same PCE (27.78%), indicating that the CeOx ETL is dispensable for a simplified, and cost-effective design. The achieved efficiency exceeds previous reports on Cs?TiBr?-based PSCs