Over 19% Efficiency Perovskite Solar Modules by Simultaneously Suppressing Cation Deprotonation and Iodide Oxidation

Perovskite solar cells (PSCs) based on sputtered nickel oxide (NiO_x) hole transport layer have emerged as promising configuration due to their good stability, cost-effectiveness, and scalability. However, the adverse chemical redox reaction at the NiO_x/perovskite interface remains an ever-present problem that has not yet been well solved. To address this issue before, the problems that cation deprotonation and iodide oxidation that occurred in precursor solution easily result in the interfacial chemical reaction should be prevented. Hence, we report an efficient strategy to simultaneously suppress the interfacial reaction and stabilize the precursor solution by incorporating a reducing and weakly acidic stabilizer, l-ascorbic acid (l-AA). l-AA can reduce I₂ generated in the precursor solution and during the interfacial reaction to I^-. Furthermore, the protons ionized by adjacent enol hydroxyl groups in l-AA effectively impede the deprotonation of organic cations in the precursor solution as well as at the NiO_x/perovskite interface resulting from the chemical reaction. Attributing to the improved crystallization of the perovskite film and the suppression of the interfacial reaction by l-AA, the inverted PSC based on such good light absorber achieves an impressive power conversion efficiency (PCE) of 22.72% along with a high open-circuit voltage of 1.19 V. Notably, further introducing l-AA into the large-area solar modules by the slot-die coating method in air enables a remarkable PCE of 19.17%, which reaches one of the highest PCEs reported for inverted perovskite solar modules (PSMs) (active area >50 cm²) to date. l-AA located at the buried interface also forms a barrier layer that can prevent undesirable chemical reactions at the NiO_x/perovskite interface, significantly enhancing the device stability of solar cells and PSMs. These findings in our work provide important guidance for improving the NiO_x/perovskite interface and the fabrication of highly efficient, low-cost, and large-area PSMs.