Unveiling the prospect of copper iodide as hole transporting layer in perovskite solar cell by selective dopant strategy: A review

The burgeoning field of perovskite solar cells (PSCs) continues to attract research interest, particularly with the potential of copper iodide (CuI) as a high-performing hole transport layer (HTL). This review comprehensively examines the intrinsic advantages of solid-state CuI as HTL for PSC applications due to its exceptional p-type conductivity, ambient stability, and ease of synthesis. Moreover, the review explores cutting-edge strategies for mitigating defects to preserve the power conversion efficiency (PCE) and stability of the device including optimization of synthesis, defect engineering through stoichiometry control, interface engineering and doping engineering. Notably, lanthanum (La) doping engineering on CuI demonstrates remarkable potential, offering enhanced structural compatibility due to its ionic size, improved band alignment, and a substantial reduction in deep-level traps contributing to carrier recombination. This groundbreaking doping strategy produces La-doped CuI HTL that addresses the challenges at the perovskite/HTL interface, leading to an elevation in the PCE of the PSCs. As PSC technology advances toward commercial viability, CuI emerges as a linchpin in accelerating progress in the quest for highly efficient and stable solar energy solutions.