Conjugated Pyrazine Hydrazine Small Molecules Enable Heavy N‐Type Degenerate Doping of Inorganic Perovskites

Inorganic perovskites have attracted considerable attention in photovoltaic applications owing to their ideal tunable bandgaps and exceptional photothermal stability, rendering them a leading candidate for light‐absorbing materials in next‐generation perovskite solar cells. However, pure‐phase CsPbI 3 perovskite thin films suffer from crystalline disorder, high surface defect density, severe non‐radiative carrier recombination, and excessive open‐circuit voltage loss, collectively imposing severe limitations on both the power conversion efficiency ( PCE ) and environmental stability of the resulting optoelectronic devices. This work employs 2‐hydrazinopyrazine (Hdzpz) as a functional additive, leveraging the synergistic effect between its pyrazine‐based conjugated backbone and dual active nitrogen sites on the hydrazine group to rationally modulate the nucleation and growth kinetics, microstructural morphology, energy‐level alignment, interfacial properties, and hydrophobicity of CsPbI 3 perovskite thin films. This strategy effectively passivates undercoordinated lead defects and halide vacancies within the perovskite lattice. Meanwhile, CsPbI 3 is driven into a degenerate semiconductor state, yielding a heavily n‐type degenerately doped perovskite, thereby enhancing interfacial charge‐carrier transport efficiency. Ultimately, a PCE of 20.80% is achieved, accompanied by significantly improved photothermal and moisture stability.