Morphology of highly stable lead-free hybrid organic–inorganic double perovskites (CH3NH3)2XBiCl6 (X = K, Na, Ag) for solar cell applications

The power conversion efficiency (PCE) of single structured perovskite solar cells (PSCs) has achieved a remarkable value of 25.2% over the last ten years. But these PSCs are not eco-friendly and suffer from the serious issue of stability. So it is very important to investigate greener and more stable alternatives to these perovskite materials. In recent years, lead-free double perovskite (DP) materials have surfaced as an ecologically favorable photovoltaic material due to their inherent chemical stability, modest carrier effective masses, suitable bandgaps, and low exciton binding energies. Herein, we have synthesized lead-free, highly stable, good quality, cheaper and environment friendly halide-based hybrid organic–inorganic double perovskite (MA)2XBiCl6 (MA = CH3NH3, X = K, Na, Ag) by adopting one step hydrothermal route having the morphology of vertical flakes and micro-rods. Further, we have analyzed the morphological, photophysical, chemical, electronic, and structural behavior of synthesized samples by using various characterization techniques. We elucidated the formation of high-quality, stable, and highly crystalline luminescent DP nanoparticles (NPs). Moreover, we fabricated three solar cell devices using the three as-synthesized DPs and further demonstrated that the solar cell device using MA2NaBiCl6 NPs as absorber layer have 2.09% PCE performed better as compared to MA2KBiCl6 and MA2AgBiCl6 based devices. Our work reports a first lead-free double perovskite solar cell with different three-dimensional morphology shedding light on the shape manipulation and providing a feasible alternative to toxicity issues in single perovskite and further encouraging rigorous research on these materials for future photovoltaic technology.