Highly Efficient and Stable Perovskite Solar Cell via Semiconducting Chemical Additive Cyclized Polyacrylonitrile

Solution-processed organic-inorganic hybrid perovskite films suffer from halide vacancies, uncoordinated lead cations (Pb²⁺), and excessive iodide at surfaces and grain boundaries, inducing non-radiative recombination, hysteresis, and energy loss. In this study, cyclized polyacrylonitrile (CPAN) was introduced as a multifunctional semiconductor additive into the perovskite, effectively regulating the crystallization and passivating defects of perovskite films. The cyano group (C≡N) and carbonyl groups (C═O) in CPAN effectively suppressed the premature nucleation of lead iodide (PbI₂) clusters via their interaction, minimizing the formation of δ-phase perovskite facilitating the formation of larger, more homogeneous grains and thus favoring oriented crystal growth. In the meanwhile, the Pb defects and shallow-level iodine vacancy defects in the film were passivated via strong-coordinating C≡N and moderately coordinating C═O. Furthermore, the CPAN semiconductor with high electron mobility enables well-aligned perovskite energy band structures, facilitating charge extraction. Additionally, the inherent hydrophobic nature of the cyano group (C≡N) created a water-resistant barrier at grain boundaries, significantly inhibiting the penetration of moisture into the perovskite film. Consequently, the power conversion efficiency of the perovskite solar cells (PSCs) increased from 20.56 to 22.38%, while the open-circuit voltage rose from 1.08 to 1.11 V. Notably, after 900 h of storage under ambient conditions without illumination, the initial efficiency of PSCs was retained at 84%, demonstrating a marked enhancement in operational stability. This work presents a novel strategy for controlling the crystal orientation and fabricating high-performance PSCs.