Publication date: 5th November 2025
Electron-transport-layer-free (ETL-free) perovskite solar cells (PSCs) combine structural simplicity with high efficiency, making them ideal for tandem applications as top cells. While most efforts have improved performance by modifying the fluorine-doped tin oxide (FTO)/perovskite interface, the role of the perovskite/hole transport layer (HTL) interface has been largely overlooked. Here, we enhance charge collection in ETL-free PSCs by tuning the internal electric field through both bulk perovskite optimization and interface engineering [1]. Using excess PbI₂ doping and annealing to control carrier properties, we improve the perovskite’s electronic behavior. A multifunctional 2D-perovskite interlayer further passivates surface defects and introduces a built-in electric field, similar to the n/p/p⁺ back-surface field found in silicon solar cells. Cross-sectional Kelvin probe force microscopy (KPFM) reveals the mechanism of this interfacial field. The optimized devices reach a record 22.47 % power conversion efficiency, without any FTO modification or extra interlayers, and retain 75 % of their performance after 1100 hours in a humid (≈50 ± 5 % RH) dark environment. This work demonstrates a practical route toward efficient, durable, and scalable ETL-free perovskite solar cells.
This study was supported by the National Research Foundation of Korea (NRF) under grants RS-2025-00522430, RS-2025-02316700, and RS-2023-00259096. Additional support was provided by the Korea Research Institute of Chemical Technology (KRICT) under project No. KS2522-30.
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