Interfacial Engineering with One-Dimensional Lepidocrocite TiO₂-Based Nanofilaments for High-Performance Perovskite Solar Cells

The optimization of nonradiative recombination losses through interface engineering is key to the development of efficient, stable, and hysteresis-free perovskite solar cells (PSCs). In this study, for the first time in solar cell technology, we present a novel approach to interface modification by employing one-dimensional lepidocrocite (henceforth referred to as 1DL) TiO₂-based nanofilaments, NFs, between the mesoporous TiO₂ (mp TiO₂) and halide perovskite film in PSCs to improve both the efficiency and stability of the devices. The 1DLs can be easily produced on the kilogram scale starting with cheap and earth-abundant precursor powders, such as TiC, TiN, TiB₂, etc., and a common organic base like tetramethylammonium hydroxide. Notably, the 1DL deposition influenced perovskite grain development, resulting in a larger grain size and a more compact perovskite layer. Additionally, it minimized trap centers in the material and reduced charge recombination processes, as confirmed by the photoluminescence analysis. The overall promotion led to an improved power conversion efficiency (PCE) from 13 ± 3.2 to 16 ± 1.8% after interface modification. The champion PCE for the 1DL-containing devices is 17.82%, which is higher than that of 16.17% for the control devices. The passivation effect is further demonstrated by evaluating the stability of PSCs under ambient conditions, wherein the 1DL-containing PSCs maintain ∼87% of their initial efficiency after 120 days. This work provides not only cost-effective, novel, and promising materials for cathode interface engineering but also an effective approach to achieve high-efficiency PSCs with long-term stability devoid of encapsulation.