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Vol. 18 (2026)

Vertical Interfacial Engineering in Two-Step-Processed Perovskite Films Enabled by Dual-Interface Modification for High-Efficiency p-i-n Solar Cells

https://doi.org/10.1007/s40820-025-02010-w
Wenhao Zhou
School of New Energy, Ningbo University of Technology, Ningbo 315211, People’s Republic of China
Heng Liu
Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People’s Republic of China
Haiyan Li
Siyuan Laboratory, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Department of Physics, Jinan University, Guangzhou 510632, People’s Republic of China
Weihai Zhang
School of New Energy, Ningbo University of Technology, Ningbo 315211, People’s Republic of China
Hui Li
School of New Energy, Ningbo University of Technology, Ningbo 315211, People’s Republic of China
Xia Zhou
School of New Energy, Ningbo University of Technology, Ningbo 315211, People’s Republic of China
Rouxi Chen
School of Innovation and Entrepreneurship, Southern University of Science and Technology, Shenzhen 518055, People’s Republic of China
Wenjun Zhang
School of New Energy, Ningbo University of Technology, Ningbo 315211, People’s Republic of China
Tingting Shi
Siyuan Laboratory, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Department of Physics, Jinan University, Guangzhou 510632, People’s Republic of China
Antonio Abate
School of New Energy, Ningbo University of Technology, Ningbo 315211, People’s Republic of China
Hsing‑Lin Wang
Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People’s Republic of China

Corresponding Author: Hsing‑Lin Wang

wangxl3@sustech.edu.cn

Nano-Micro Letters, Vol. 18 (2026), Article Number: 157

Abstract

Two-step-processed (TSP) inverted p-i-n perovskite solar cells (PSCs) have demonstrated significant promise in tandem applications. However, the power conversion efficiency (PCE) of TSP p-i-n PSCs rarely exceeds 24%. Here, we demonstrate that TSP perovskite films exhibit a vertically gradient distribution of residual PbI2 clusters, which form Schottky heterojunctions with the perovskite, leading to substantial interfacial energy-level mismatches within NiOx-based TSP p-i-n PSCs. These limitations were effectively addressed via a vertical interfacial engineering enabled by dual-interface modification incorporating tin trifluoromethanesulfonate (Sn(OTF)2) and 4-Fluorophenylethylamine chloride (F-PEA) at the NiOx/perovskite and perovskite/C60 interfaces, respectively. The functional Sn(OTF)2 not only enhances the conductivity of NiOx films but also suppresses ion migration, while inducing the formation of a Pb-Sn mixed perovskite interlayer that precisely regulates the energy level at the NiOx/perovskite interface. Complementally, F-PEA post-treatment effectively converts surface residual PbI2 clusters into a 2D perovskite capping layer, which simultaneously passivates surface defects and enhances energy-level alignment at the perovskite/C60 interface. Consequently, the optimized NiOx-based TSP p-i-n PSCs achieve a notable PCE of 25.6% with superior operational stability. This study elucidates the underlying mechanisms limiting the efficiency of TSP p-i-n PSCs, while establishing design principles for these devices targeting 26% efficiency.


Highlights:
1 A vertical interfacial engineering strategy via dual-interface modification (Sn(OTF)2 at NiOx/perovskite, 4-Fluorophenylethylamine chloride (F-PEA) at perovskite/C60) solves energy-level mismatches in two-step-processed (TSP) p-i-n PSCs, boosting PCE to 25.6%.
2 Sn(OTF)2 enhances NiOx conductivity, suppresses ion migration, and forms a Pb-Sn perovskite interlayer; F-PEA eliminates PbI2, forming a 2D capping layer for defect passivation.
3 Optimized NiOx-based TSP p-i-n PSCs retain 84% initial power conversion efficiency after 720-h light illumination, providing design principles for 26%-efficiency devices.

Keywords

Vertical interfacial engineering Interface modification Energy-level modulation Nickle oxide Two-step procession
Zhou, Wenhao, Heng Liu, Haiyan Li, Weihai Zhang, Hui Li, Xia Zhou, Rouxi Chen, Wenjun Zhang, Tingting Shi, Antonio Abate, and Hsing‑Lin Wang. 2026. “Vertical Interfacial Engineering in Two-Step-Processed Perovskite Films Enabled by Dual-Interface Modification for High-Efficiency P-I-N Solar Cells”. Nano-Micro Letters 18 (January):157. https://doi.org/10.1007/s40820-025-02010-w.
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