Capillary-written single-crystalline all-inorganic perovskite microribbon arrays for highly-sensitive and thermal-stable photodetectors

Highly luminescent and stable CsPbBr3 perovskite nanocrystals coated with polyethersulfone for white light-emitting diode applications

Simultaneously improving the stability and photoluminescence quantum yield (PLQY) of all inorganic perovskite nanocrystals (NCs) is crucial for their practical utilization in various optoelectronic devices. Here, CsPbBr3 NCs coated with polyethersulfone (PES) were prepared via an in-situ co-precipitation method. The sulfone groups in PES bind to undercoordinated lead ion (Pb2+) on the CsPbBr3 NCs, resulting in significant reduction of surface defects, thus enhancing the PLQY from 74.2% to 88.3%. Meanwhile, the PES-coated NCs exhibit high water resistance and excellent heat and light stability, maintaining over 85% of the initial PL intensity under thermal aging (70°C, 4 h) and continuous 365 nm ultraviolet (UV) light irradiation (24 W, 8 h) conditions. By contrast, the PL intensity of the control NCs dramatically dropped to less than 40%. Finally, a diode emitting bright white light was fabricated utilizing the PES-coated CsPbBr3 NCs, which exhibits a color gamut of ~110% NTSC standard.

High Responsivity Circular Polarized Light Detectors based on Quasi Two-Dimensional Chiral Perovskite Films

Circularly polarized light (CPL) has considerable technological potential, from quantum computing to bioimaging. To maximize the opportunity, high performance photodetectors that can directly distinguish left-handed and right-handed circularly polarized light are needed. Hybrid organic-inorganic perovskites containing chiral organic ligands are an emerging candidate for the active material in CPL photodetecting devices, but current studies suggest there to be a trade-off between the ability to differentially absorb CPL and photocurrent responsivity in chiral perovskites devices. Here, we report a CPL detector based on quasi two-dimensional (quasi-2D) chiral perovskite films. We find it is possible to generate materials where the circular dichroism (CD) is comparable in both 2D and quasi-2D films, while the responsivity of the photodetector improves for the latter. Given this, we are able to showcase a CPL photodetector that exhibits both a high dissymmetry factor of 0.15 and a high responsivity of 15.7 A W^-1. We believe our data further advocates the potential of chiral perovskites in CPL-dependent photonic technologies.

Advancing 2D Perovskites for Efficient and Stable Solar Cells: Challenges and Opportunities

Perovskite solar cells (PSCs) have rapidly emerged as one of the hottest topics in the photovoltaics community owing to their high power-conversion efficiencies (PCE), and the promise to be produced at low cost. Among various PSCs, typical 3D perovskite-based solar cells deliver high PCE but they suffer from severe instability, which restricts their practical applications. In contrast to 3D perovskites, 2D perovskites that incorporate larger, less volatile, and generally more hydrophobic organic cations exhibit much improved thermal, chemical, and environmental stability. 2D perovskites can have different roles within a solar cell, either as the primary light absorber (2D PSCs), or as a capping layer atop a 3D perovskite absorbing layer (2D/3D PSCs). Tradeoffs between PCE and stability exist in both types of PSCs-2D PSCs are more stable but exhibit lower efficiency while 2D/3D PSCs deliver exciting efficiency but show relatively poor stability. To address this PCE/stability tradeoff, the challenges both the 2D and 2D/3D PSCs face are identified and select works the community has undertaken to overcome them are highlighted in this review. It is ended with several recommendations on how to further improve PSCs so their performance and stability can be commensurate with application requirements.

Polyhydroxy Ester Stabilized Perovskite for Low Noise and Large Linear Dynamic Range of Self-Powered Photodetectors

Solution-processed perovskites as emerging semiconductors have achieved unprecedented milestones in sensor optoelectric devices. Stability along with the device noise issues are the major obstacle for photodetectors to compete with the traditional devices. Here, we demonstrated that l-ascorbic acid (l-AA) as a polyhydroxy ester can coordinate with the amino group of formamidine cations (FA⁺) through multiple hydrogen bond interactions to stabilize the perovskite, which protect the FA⁺ ions from nucleophile attack and effectively suppress the degradation of FA⁺ ions, improving the perovskite stability and suppressing the device noise to below 0.3 pA Hz^-1/2 with a large linear dynamic range of 239 dB. The dual functions of l-AA enable the perovskite photodetector to have a high detectivity of 10¹² Jones. The self-powered device works with no energy consumption and maintains an undegraded performance over 1200 h of inspection at ambient conditions, which is promising for infrastructure construction, signal sensing, and real-time information delivery.

Accessing Highly Oriented Two-Dimensional Perovskite Films via Solvent-Vapor Annealing for Efficient and Stable Solar Cells

Accessing vertical orientation of two-dimensional (2D) perovskite films is key to achieving high-performance solar cells with these materials. Herein, we report on solvent-vapor annealing (SVA) as a general postdeposition strategy to induce strong vertical orientation across broad classes of 2D perovskite films. We do not observe any local compositional drifts that would result in impure phases during SVA. Instead, our experiments point to solvent vapor plasticizing 2D perovskite films and facilitating their surface-induced reorientation and concomitant grain growth, which enhance out-of-plane charge transport. Solar cells with SVA 2D perovskites exhibit superior efficiency and stability compared to their untreated analogs. With a certified efficiency of (18.00 ± 0.30) %, our SVA (BDA)(Cs_0.1FA_0.9)₄Pb₅I₁₆ solar cell boasts the highest efficiency among all solar cells with 2D perovskites (n ≤ 5) reported so far.

Millimeter-Sized Single-Crystal CsPbrB3/CuI Heterojunction for High-Performance Self-Powered Photodetector

Millimeter-sized CsPbBr₃ single crystals were prepared via a facile solvent-evaporation method in ambient environment. The heterojunction between p-type CuI and n-type CsPbBr₃ was formed by a simple immersion process. The as-integrated CsPbBr₃/CuI device exhibits a good rectifying behavior (ratio of 250 at ±2 V). In particular, the photodetector shows excellent self-powered characteristics under 540 nm light illumination, including high photocurrent (near 100 nA); high photosensitivity (on/off ratio of 1.5 × 10³); fast response speed (0.04/2.96 ms); and good wavelength selectivity (565-525 nm), responsivity (1.4 mA W^-1), and detectivity (6.2 × 10¹⁰ Jones). This work provides a simple, low-cost, and effective method for preparing millimeter-level CsPbBr₃ single crystals. The simple device architecture further provides a promising approach for fabricating high-performance self-powered photodetectors.