Design and optimization of lead-free double-absorber perovskite solar cells using Cs2PtI6 and Cs2TiI6

• A fully lead-free double-absorber PSC using Cs 2 PtI 6 and Cs 2 TiI 6 is designed. • SCAPS-1D optimization yields a high PCE of 35.63% with strong device stability. • Complementary absorber bandgaps enable broad light harvesting from 300–910 nm. • Detailed ETL and HTL screening identifies TiO 2 and CuO as optimal layers. • Defect, thickness, and temperature analyses reveal key performance limits. • Results offer a practical pathway toward stable and non-toxic perovskite photovoltaics. The global search for clean and sustainable energy has placed perovskite solar cells (PSCs) at the forefront of photovoltaic research. Their rapid rise in efficiency has been remarkable, yet two persistent challenges lead toxicity and poor long-term stability—continue to hinder practical deployment. In this work, we take a step toward solving both problems by designing a fully lead-free double-absorber PSC that combines the strengths of Cs 2 PtI 6 and Cs 2 TiI 6 . Using SCAPS-1D simulations, we explored a wide range of material choices and device parameters to uncover an optimal architecture. The best-performing configuration, FTO/TiO 2 /Cs 2 PtI 6 /Cs 2 TiI 6 /CuO/Au, delivered a power conversion efficiency of 35.63%, supported by high current density (32.90 mA/cm 2 ), open-circuit voltage (1.234 V), and fill factor (87.73%). Beyond efficiency, this design exhibited broad-spectrum absorption (300–910 nm), strong resistance to thermal and environmental stress, and excellent tolerance to defect traits that are essential for long-term operation. The combination of the narrow-bandgap Cs 2 PtI 6 (1.37 eV) with the wider-bandgap Cs 2 TiI 6 (1.65 eV) ensures complementary light harvesting and reduced recombination losses, outperforming single-absorber devices. By uniting high efficiency, stability, and environmental safety, this work highlights the potential of Cs 2 PtI 6 /Cs 2 TiI 6 double absorbers to drive the next generation of sustainable solar technology.