Magnesium-Doped Nickel Oxide Hole Transport Layer Achieves High Efficiency and Stability Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) are promising thin-film photovoltaic devices and achieve a high power conversion efficiency (PCE) of 27.3% (certified). Hole transport layer (HTL) composed of nickel oxide (NiO_x) and [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) is extensively utilized in these devices. However, the dispersion and conductivity of NiO_x are suboptimal, and it exhibits energy-level mismatch. Meanwhile, the coverage of Me-4PACz on NiO_x is non-uniform. Herein, we synthesized magnesium ion-doped nickel oxide (Mg:NiO_x) with more surface hydroxyl groups to address these issues. More surface hydroxyl groups provided more binding sites for Me-4PACz, resulting in a denser and more uniform coverage of Me-4PACz. Consequently, fewer defects were present at the buried interface, and a better environment for the crystallization of perovskite (PVK) was established. Furthermore, Mg:NiO_x/Me-4PACz enabled better energy level alignment with PVK. The Mg:NiO_x-based PSCs achieved a champion PCE of 25.86%, representing a notable improvement over the NiO_x-based devices (24.51%). After 462 h of continuous illumination testing, the PSCs with Mg:NiO_x retained 96.8% of their initial PCE, while those with NiO_x only maintained 62.9% of their initial PCE. Thus, Mg:NiO_x effectively enhanced both the PCE and stability of PSCs.

Keywords

Mg-doped NiO_x / Hole transport layer / Hydroxyl groups / Defect passivation / Non-radiative voltage loss / Power conversion efficiency / Stability / Perovskite solar cells

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2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH