The improvement in double perovskite solar cells Cs2AgBiBr6 by the praseodymium doping and surface passivation of polythiophene

Lead-free double perovskite solar cells, particularly Cs₂AgBiBr₆, have emerged as crucial alternatives to toxic lead-based perovskites in the pursuit of environmentally sustainable photovoltaics. Their design and fabrication address critical needs for non-toxic, stable solar cell materials that can be deployed in diverse applications ranging from building-integrated photovoltaics to portable electronic devices. This study presents an optimized device architecture combining poly(3-hexylthiophene) (P3HT) as a dopant-free hydrophobic hole transport material with Praseodymium-doped Cs₂AgBiBr₆ to overcome inherent challenges of wide bandgaps and high defect densities. Comprehensive characterization validates the enhanced performance, with Pr doping reducing the bandgap from 2.15 eV to 1.93 eV and P3HT passivation increasing grain size to 37.7 nm while lowering dislocation density to 6.51 × 10¹⁶ cm⁻³. The optimized devices demonstrate a power conversion efficiency of 3.98 %, a significant improvement over undoped counterparts (3.46 %), with exceptional stability retaining 95 % of initial PCE after 1,300 h under ambient conditions. These results are rigorously validated through current–voltage measurements, defect density analysis, and long-term stability testing under operational conditions. The work establishes a viable pathway for developing high-performance lead-free perovskite solar cells suitable for practical applications in both outdoor and indoor photovoltaic systems, marking an important advancement toward commercially viable, eco-friendly solar technologies.