One‐Step Synthesis of Lead‐Free and Hole Transport Layer‐Free Methylammonium Bismuth Chloride ((CH3NH3)3Bi2IxCl9−x)‐Based Perovskite Solar Cells

The scientific community is moving toward a green environment using several nontoxic photon‐absorbing materials like tin, germanium, antimony, and bismuth. Bismuth halides have essential advantages like low toxicity, Earth abundance, good chemical stability, and optoelectronic behavior which make them suitable for lead‐free perovskite solar cells. Herein, a streamlined one‐step spin‐coating technique is employed using DMF to enhance the morphology of thin films based on BiCl 3 perovskite. The resulting thin films of methylammonium bismuth halide ((CH 3 NH 3 ) 3 Bi 2 I x Cl 9− x ) display a remarkably uniform, pinhole‐free, and finely nanostructured morphology, ensuring consistent surface coverage. For the development of hole conductor‐free Bi‐perovskite solar cells (PSCs), carbon is utilized as both counter electrode and hole extraction layer. The device configuration entails FTO/Compact TiO 2 /meso‐TiO 2 /((CH 3 NH 3 ) 3 Bi 2 I x Cl 9− x )/Carbon/FTO, a novel arrangement for Bi‐PSCs. Notably, the fabricated devices demonstrate commendable photovoltaic properties, including V oc of 280 mV, J sc of 0.25 mA, fill factor of 0.60, and a notably elevated power conversion efficiency (PCE) of 0.042% which has proven significantly advantageous in achieving higher PCE. Furthermore, the fabricated devices exhibit robust chemical stability over 40 d when exposed to an ambient atmosphere without encapsulation. The solar cells retain 25% of their initial PCE after 168 h, further highlighting their durability and suitability for practical applications.