Hydroxyl‐Rich Sodium Gluconate Enables Dense SAM Assembly and Enhances Conductivity in NiO x ‐Based Inverted Perovskite Solar Cells

ABSTRACT Nickel oxide (NiO x )/self‐assembled monolayer (SAM) composite hole transport layers represent a promising configuration for inverted perovskite solar cells (IPSCs). Nevertheless, the insufficient electrical conductivity of NiO x and the limited number of binding sites on its surface lead to incomplete monolayer coverage, resulting in substantial interfacial charge losses that constrain efficiency improvements. To address these issues, we introduce hydroxyl‑rich sodium gluconate (SG) into the NiO x solution. Gluconate anions from SG modulate the electronic properties of NiO x , thereby enhancing its conductivity. Meanwhile, the abundant hydroxyl groups along the SG backbone furnish additional hydrogen‐bonding sites for the subsequent adsorption of the SAM, promoting the formation of a compact and well‐ordered interfacial molecular layer. This dense SAM not only suppresses leakage currents but also optimizes the energetic cascade at the heterojunction, ultimately enabling the resulting IPSCs to achieve a power conversion efficiency of 26.24%. During maximum‐power‐point operation under ISOS‑L‑1 protocol, the optimized device preserves 91.6% of the starting output after 1000 h. This work establishes a versatile interfacial engineering approach that overcomes limitations in both SAM assembly and charge transport, offering new opportunities for the development of highly efficient and durable IPSCs.

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