In recent years, organic−inorganic hybrid perovskite solar cells (PSCs) have attracted extensive attention due to their high power conversion efficiency (PCE) and simple preparation process. The selection and optimization of the hole transport layer (HTL) are very important for device performance. Compared to other HTLs, nickel oxide (NiO x ) has been widely used in PSCs due to its good chemical stability, high hole mobility, and simple preparation method. This review begins with the application of NiO x HTL in planar PSCs and systematically introduces the influence of the structure and photoelectrical properties of devices by doping and surface modification. The effects of NiO x modification on the power conversion efficiency (PCE), filling factor (FF), open-circuit voltage (V oc ), short-circuit current (J sc ), and stability of PSCs are reviewed in detail from the perspectives of energy-level matching, hole mobility, and crystallinity. Finally, the future of NiO x -based planar PSCs is discussed.

Given the advantages of high power conversion efficiencies (PCEs), antisolvent-step free production, and suitability for device production in ambient conditions, perovskite solar cells (PSCs) based on ionic-liquid solvents have attained particular research interest. To further improve device performance, light management could be optimized to increase light harvesting in the perovskite layer. Here, ordered honeycomb-like TiO 2 (Hc-TiO 2 ) structures with a periodicity of around 450 nm were fabricated through a sacrificial template method. With this photonic crystal structure, the control to light flow and the confinement effect for perovskite growth were achieved simultaneously in the Hc-TiO 2 , leading to improved light absorption as well as preferred crystal orientation. Furthermore, a reduced trap-state density and a well-aligned energy level induced by the perovskite/pore interlayer facilitated the chargecarrier extraction from the perovskite layer to electron transport layer. As a result, the structured devices performed better than the planar cells. And the angular dependent J-V sweeps show that the structured device reserved 76 % of its initial short circuit current density (J sc ), whereas the planar cell showed more than a half loss under the incident light of 40°, demonstrating a reduced downward trend in J sc with the presence of photonic crystal structures. This occurrence also suggests that the structured PSCs in this work have a high tolerance to optical path changes.

Luminescent solar concentrators (LSCs) are capable of absorbing solar light over a large area, which subsequently converts light into luminescence at a red-shifted wavelength and then redirects it to a smaller target to increase the per-unit yield of photovoltaic devices. Among various LSC materials, perovskite nanocrystals (NCs) have attracted great attention due to their adjustable band gap, multi-exciton effect, and good stability. In this review, a brief introduction of LSCs, including their advances and principles, is given, followed by a summary of perovskite-NCs-based LSCs. The selected examples for component optimization of inorganic perovskite NCs are outlined after an introduction to the structure and properties of perovskite NCs. The absorption and/or emission peaks of all-inorganic and inorganic-organic hybrid perovskite NCs can be efficiently regulated, which not only increases the Stokes shift but also improves the stability. Excellent performance and operability show a bright application prospect of perovskite NCs in the field of LSC applications.

Perovskite nanocrystals (PNCs) with unique and excellent optical properties have emerged as appealing luminescent materials in optoelectronic fields. However, high temperature processing, complicated procedures, and the use of toxic solvents are typically involved in the preparation of PNCs and their related optoelectronic devices. In this study, a one‐step method is developed for the preparation of flexible photoluminescence gel based on PNCs at ambient conditions, which is a promising alternative to the current PNCs preparation strategy in terms of experimental friendliness, ease of production, and the potential for flexible devices. Acrylic acid (AA) is used for in situ crystallization of PNCs. The interaction between H+ of AA and perovskite‐solvent complex determines the nucleation and growth of PNCs. This crystallization mechanism is systematically studied by varying acid category, adjusting solvent kind, and regulating the ratio of PNCs and gels. To give a proof of practicability, flexible free‐standing PNCs‐gel composites with excellent luminescent and mechanical properties are prepared with the AA treatment. Moreover, the PNCs‐gel shape can be customized, which greatly expands the structural flexibility and functionalities of fabricated devices.