Copper-Substituted Lead Perovskite Materials Constructed with Different Halides for Working (CH₃NH₃)₂CuX₄‑Based Perovskite Solar Cells from Experimental and Theoretical View

Toxicity and chemical instability issues of halide perovskites based on organic–inorganic lead-containing materials still remain as the main drawbacks for perovskite solar cells (PSCs). Herein, we discuss the preparation of copper (Cu)-based hybrid materials, where we replace lead (Pb) with nontoxic Cu metal for lead-free PSCs, and investigate their potential toward solar cell applications based on experimental and theoretical studies. The formation of (CH₃NH₃)₂CuX₄ [(CH₃NH₃)₂CuCl₄, (CH₃NH₃)₂CuCl₂I₂, and (CH₃NH₃)₂CuCl₂Br₂] was discussed in details. Furthermore, it was found that chlorine (Cl^–) in the structure is critical for the stabilization of the formed compounds. Cu-based perovskite-like materials showed attractive absorbance features extended to the near-infrared range, with appropriate band gaps. Green photoluminescence of these materials was obtained because of Cu⁺ ions. The power conversion efficiency was measured experimentally and estimated theoretically for different architectures of solar cell devices