The light-emitting diodes (LEDs) used in indoor testing of perovskite solar cells do not expose them to the levels of ultraviolet (UV) radiation that they would receive in actual outdoor use. We report degradation mechanisms of p-i-n–structured perovskite solar cells under unfiltered sunlight and with LEDs. Weak chemical bonding between perovskites and polymer hole-transporting materials (HTMs) and transparent conducting oxides (TCOs) dominate the accelerated A-site cation migration, rather than direct degradation of HTMs. An aromatic phosphonic acid, [2-(9-ethyl-9H-carbazol-3-yl)ethyl]phosphonic acid (EtCz3EPA), enhanced bonding at the perovskite/HTM/TCO region with a phosphonic acid group bonded to TCOs and a nitrogen group interacting with lead in perovskites. A hybrid HTM of EtCz3EPA with strong hole-extraction polymers retained high efficiency and improved the UV stability of perovskite devices, and a champion perovskite minimodule—independently measured by the Perovskite PV Accelerator for Commercializing Technologies (PACT) center—retained operational efficiency of >16% after 29 weeks of outdoor testing.

Perovskite solar cells (PSCs) have witnessed astonishing improvement in power conversion efficiency (PCE), more recently, with advances in long‐term stability and scalable fabrication. However, the presence of an anomalous hysteresis behavior in the current density–voltage characteristic of these devices remains a key obstacle on the road to commercialization. Herein, sol–gel‐processed mesoporous boron‐doped TiO₂ (B‐TiO₂) is demonstrated as an improved electron transport layer (ETL) for PSCs for the reduction of hysteresis. The incorporation of boron dopant in TiO₂ ETL not only reduces the hysteresis behavior but also improves PCE of the perovskite device. The simultaneous improvements are mainly ascribed to the following two reasons. First, the substitution of under‐coordinated titanium atom by boron species effectively passivates oxygen vacancy defects in the TiO₂ ETL, leading to increased electron mobility and conductivity, thereby greatly facilitating electron transport. Second, the boron dopant upshifts the conduction band edge of TiO₂, resulting in more efficient electron extraction with suppressed charge recombination. Consequently, a methylammonium lead iodide (MAPbI₃) photovoltaic device based on B‐TiO₂ ETL achieves a higher efficiency of 20.51% than the 19.06% of the pure TiO₂ ETL based device, and the hysteresis is reduced from 0.13% to 0.01% with the B‐TiO₂ based device showing negligible hysteresis behavior.

The two-dimensional (2D) perovskite (including pure-2D and quasi-2D) is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were widely developed with the enriched species and advanced physical-knowledge in material characteristics as well as optoelectronic device applications. To review achievments in 2D perovskite, the fundamental mechanism and properties of 2D perovskite are introduced to offer insight into device performance. Moreover, the preparation methods of 2D perovskite films are summarized and compared. The latest successful applications of the 2D perovskite in the solar cells and light-emitting diodes fields, especially the advanced stability of 2D perovskite solar cells (PeSCs) and the efficient 2D perovskite light-emitting diodes (PeLEDs), are also achieved. Furthermore, the challenges and outlook of 2D perovskite materials are proposed. 二维(2D)钙钛矿材料(包括纯2D和准2D)是在传统意义上的三维钙钛矿晶格中插入大基团卤化铵形成的. 在过去的20年里, 二维钙钛矿材料种类不断丰富, 相关理论研究不断深入, 在光电器件领域的应用不断拓展. 本综述介绍了2D钙钛矿材料的基本形成机制和性能, 汇总和比较了2D钙钛矿薄膜的制备方法, 并给出了其在太阳电池以及发光二极管领域的应用实例. 最后, 提出了该领域亟待解决的问题, 以及未来的研究趋势.

Phosphonic acid (PA)–based interlayers used in metal-halide perovskite solar cells (PSCs) can suffer from instability at elevated temperatures. We report that the acidic protons of PAs weakly bound to indium tin oxide (ITO) can accelerate the oxidation of iodide, decomposition of formamidinium, and reduction of lead ions and that these reactions accelerate at high temperature and on exposure to ultraviolet light. Also, some common PA molecules weakly bonded to ITO can desorb and react with perovskites. We synthesized a bis(diarylamino)biphenyl-based PA that binds more strongly to ITO and show that its use in PSCs led to an operational lifetime of nearly 3000 hours with 10% efficiency loss (T ₉₀ ) at 85°C under a metal halide lamp (including ultraviolet light) with maximum power point tracking. Minimodules had power conversion efficiencies >22% with an aperture area of >20 square centimeters and exhibited a T ₉₀ lifetime of ~2200 hours under similar testing conditions.

A low-temperature-processed C₆₀/ultrathin-TiO₂ bilayer is successfully designed as an ETL for high-performance and UV-stable perovskite solar cells (1 cm²).