More Like this

1. Two-dimensional halide perovskites featuring semiconducting organic building blocks

   https://doi.org/10.1039/d0qm00233j  

   Gao, Yao; Wei, Zitang; Hsu, Sheng-Ning; Boudouris, Bryan W.; Dou, Letian (January 2020, Materials Chemistry Frontiers)

   Two-dimensional (2D) organic–inorganic hybrid halide perovskites exhibit unique properties, such as long charge carrier lifetimes, high photoluminescence quantum efficiencies, and great tolerance to defects. Over the last several decades tremendous progress has occurred in the development of 2D layered halide perovskite semiconductor materials and devices. Chemical functionalization of 2D halide perovskites is an effective approach for tuning their electronic properties. A large amount of effort has been made in compositional engineering of the cations and anions in the perovskite lattice. However, few efforts have incorporated rationally designed semiconducting organic moieties into these systems to alter the overall chemical and optoelectronic properties of 2D perovskites. In fact, incorporation of large conjugated organic groups in the spatially confined inorganic perovskite matrix was found to be challenging, and this synthetic challenge hinders a deeper understanding of the materials’ structure–property relationships. Recently, exciting progress has been made regarding the molecular design, optical characterization, and device fabrication of novel 2D halide perovskite materials that incorporate functional organic semiconducting building blocks. In this article, we provide a timely review regarding this recent progress. Moreover, we discuss successes and current challenges regarding the synthesis, characterization, and device applications of such hybrid materials and provide a perspective on the true future promise of these advanced nanomaterials. 

   more » « less
2. Self-powered photodetectors based on Ruddlesden–Popper 2D hybrid perovskites with carbazole derivatives

   https://doi.org/10.1063/5.0179297  

   Alphenaar, Anna Niamh; Zhang, Xiaoyu; Xu, Yuanze; Ramakrishnan, Shripathi; Zhang, Yugang; Yu, Qiuming (December 2023, Applied Physics Letters)

   Recently, carbazole-based organic cations have garnered interest for their potential application in two-dimensional (2D) layered hybrid perovskite solar cells because of their strong hole extraction and transport as well as humidity resistance. However, the potential incorporation of carbazole-based Ruddlesden–Popper 2D hybrid perovskites in photodetectors has been largely unexplored. In this study, we synthesized ammonium 1-(9H-carbazol-9-yl) ethanaminium iodide (CzEAI) and fabricated (CzEA)2PbI4 2D perovskite thin films via varying solvent conditions to control film morphology. We constructed photodiode-type photodetectors with the active layer of (CzEA)2PbI4 2D perovskites and demonstrated a specific detectivity of 6.95 × 1010 Jones at 485 nm illumination without external bias. These results demonstrate the potential of carbazole-based 2D perovskites in a wide range of optoelectronic applications. 

   more » « less
3. Exciton Dynamics in Layered Halide Perovskite Light‐Emitting Diodes

   https://doi.org/10.1002/adma.202411998  

   Baek, Sung‐Doo; Yang, Seok Joo; Yang, Hanjun; Shao, Wenhao; Yang, Yu‐Ting; Dou, Letian (November 2024, Advanced Materials)

   Abstract Layered halide perovskites have garnered significant interest due to their exceptional optoelectronic properties and great promises in light‐emitting applications. Achieving high‐performance perovskite light‐emitting diodes (PeLEDs) requires a deep understanding of exciton dynamics in these materials. This review begins with a fundamental overview of the structural and photophysical properties of layered halide perovskites, then delves into the importance of dimensionality control and cascade energy transfer in quasi‐2D PeLEDs. In the second half of the review, more complex exciton dynamics, such as multiexciton processes and triplet exciton dynamics, from the perspective of LEDs are explored. Through this comprehensive review, an in‐depth understanding of the critical aspects of exciton dynamics in layered halide perovskites and their impacts on future research and technological advancements for layered halide PeLEDs is provided. 

   more » « less
4. Surface depletion field in 2D perovskite microplates: Structural phase transition, quantum confinement and Stark effect

   https://doi.org/10.1007/s12274-019-2524-3  

   Li, Wancai; Fang, Chen; Wang, Haizhen; Wang, Shuai; Li, Junze; Ma, Jiaqi; Wang, Jun; Luo, Hongmei; Li, Dehui (October 2019, Nano Research)

   Surface depletion field would introduce the depletion region near surface and thus could significantly alter the optical, electronic and optoelectronic properties of the materials, especially low-dimensional materials. Two-dimensional (2D) organic—inorganic hybrid perovskites with van der Waals bonds in the out-of-plane direction are expected to have less influence from the surface depletion field; nevertheless, studies on this remain elusive. Here we report on how the surface depletion field affects the structural phase transition, quantum confinement and Stark effect in 2D (BA)2PbI4 perovskite microplates by the thickness-, temperature- and power-dependent photoluminescence (PL) spectroscopy. Power dependent PL studies suggest that high-temperature phase (HTP) and low-temperature phase (LTP) can coexist in a wider temperature range depending on the thickness of the 2D perovskite microplates. With the decrease of the microplate thickness, the structural phase transition temperature first gradually decreases and then increases below 25 nm, in striking contrast to the conventional size dependent structural phase transition. Based on the thickness evolution of the emission peaks for both high-temperature phase and low-temperature phase, the anomalous size dependent phase transition could probably be ascribed to the surface depletion field and the surface energy difference between polymorphs. This explanation was further supported by the temperature dependent PL studies of the suspended microplates and encapsulated microplates with graphene and boron nitride flakes. Along with the thickness dependent phase transition, the emission energies of free excitons for both HTP and LTP with thickness can be ascribed to the surface depletion induced confinement and Stark effect. 

   more » « less
5. Design of near-perfect absorptance in few-layer WSe ₂ via cooperative enhancement mechanisms

   https://doi.org/10.1364/OME.530780  

   Ozaktas, Ekin Gunes; Chintapalli, Sreyas; Kamal, Serene; Thon, Susanna M (January 2024, Optical Materials Express)

   Two-dimensional transition metal dichalcogenides are of growing interest for flexible optoelectronics and power applications, due to their tunable optical properties, lightweight nature, and mechanical pliability. However, their thin nature inherently limits their optical absorption and, therefore, efficiency. Here, we propose a few-layer WSe₂optoelectronic device that achieves near perfect absorption through a combination of optical effects. The WSe₂can be scalably grown below an Al₂O₃superstrate. Our device includes a corrugated back reflector, modeled as a plasmonic nanowire array. We investigate the entire range of widths of the corrugations in the back reflector, including the edge cases of a simple back mirror (width equal to period) and a Fabry-Perot cavity (zero width). We demonstrate the zero-mode enhancement arising from the back reflector, the weakly coupled enhancement arising from the Fabry-Perot cavity, and the strongly coupled enhancement arising from the localized surface plasmon resonance of the nanowires, explain the physical nature of the spectral peaks, and theoretically model the hybridization of these phenomena using a coupled oscillator model. Our champion device exhibits 82% peak absorptance in the WSe₂alone, 92% in the WSe₂plus nanowires, and 98% total absorptance. Thus, we achieve a near-perfect absorber in which most of the absorption is in the few-layer WSe₂, with a desirable device framework for integration with scalable growth of the WSe₂, thereby making our designs applicable to a range of practical optoelectronic devices. 

   more » « less