ABSTRACT
Deterministic integration of phase-pure Ruddlesden-Popper (RP) perovskites has great significance for realizing functional optoelectronic devices. However, precise fabrications of artificial perovskite heterostructures with pristine interfaces and rational design over electronic structure configurations remain a challenge. Here, the controllable synthesis of large-area ultrathin single-crystalline RP perovskite nanosheets and the deterministic fabrication of arbitrary 2D vertical perovskite heterostructures are reported. The 2D heterostructures exhibit intriguing dual-peak emission phenomenon and dual-band photoresponse characteristic. Importantly, the interlayer energy transfer behaviors from wide-bandgap component to narrow-bandgap component modulated by comprising quantum wells are thoroughly revealed. Functional nanoscale photodetectors are further constructed based on the 2D heterostructures. Moreover, by combining the modulated dual-band photoresponse characteristic with double-beam irradiation modes, and introducing an encryption algorithm mechanism, a light communication system with high security and reliability is achieved. This work can greatly promote the development of heterogeneous integration technologies of 2D perovskites, and could provide a competitive candidate for advanced integrated optoelectronics.
ABSTRACT
The imitation of human visual memory demands the multifunctional integration of light sensors similar to the eyes, and image memory, similar to the brain. Although humans have already implemented electronic devices with visual memory functions, these devices require a combination of various components and logical circuits. However, the combination of visual perception and high-performance information storage capabilities into a single device to achieve visual memory remains challenging. In this study, inspired by the function of human visual memory, a dual-functional perovskite-based photodetector (PD) and memristor are designed to realize visual perception and memory capacities. As a PD, it realizes an ultrahigh self-powered responsivity of 276 mA W-1 , a high detectivity of 4.7 × 1011 Jones (530 nm; light intensities, 2.34 mW cm-2 ), and a high rectification ratio of ≈100 (±2 V). As a memristor, an ultrahigh on/off ratio (≈105 ), an ultralow power consumption of 3 × 10-11 W, a low setting voltage (0.15 V), and a long retention time (>7000 s) are realized. Moreover, the dual-functional device has the capacity to perceive and remember light paths and store data with good cyclic stability. This device exhibits perceptual and cyclic erasable memory functions, which provides new opportunities for mimicking human visual memory in future multifunctional applications.
ABSTRACT
Photodetectors (PDs) composed of lead-free metal halide perovskites have been a shining topic in optoelectronics. However, it is debatable whether perovskites are an n-type or p-type semiconductor with a direct or indirect band gap. Furthermore, to date, little research has been conducted on lead-free metal halide perovskites with color-sensing abilities. Herein, for the first time, single-crystal MA3Bi2I3xBr9-3x (x = 0, 1, 2, and 3) perovskites were systematically studied, and the results showed that MA3Bi2I9 is a p-type direct-band-gap semiconductor, whereas MA3Bi2Br9 is an n-type indirect-band-gap semiconductor. Furthermore, the band gap of MA3Bi2I3xBr9-3x (x = 0, 1, 2, and 3) perovskites can be systematically tuned from 2.06 to 2.55 eV, affording it with color-sensing abilities from 450 to 580 nm, respectively. The representative Au-MA3Bi2I9-ITO (ITO = indium tin oxide) PD exhibits a superior self-powered photodetecting performance with a high responsivity (15.8 mA W-1; 580 nm, 1.0 mW cm-2), detectivity (8.1 × 1011 Jones), an on/off ratio (4231), LDR (72.5 dB) and a fast response speed (rise time of 2 µs and decay time of 29 µs). This study not only facilitates the theoretical understanding of the band gap of perovskite materials but also sheds light on the application of lead-free perovskites in object interaction and color perception.
ABSTRACT
2D halide perovskites feature solution processability and tunable optoelectronic properties for optoelectronic applications. However, the controllable fabrication of halide perovskite heterojunction still remains a challenge. Herein, through controlling surface tension and nucleation driving force, a fast and facile aqueous floating growth is demonstrated to obtain a series of large-area single-crystalline 2D perovskite microplates at room temperature. The optoelectronic performance of 2D perovskites can be tuned by composition engineering, and the best performance is realized for quantum well index n = 4, including a suppressed dark current with boosted photocurrent and an on/off ratio up to 3.5 orders of magnitude. Benefiting from a convenient transfer method onto arbitrary substrates, vertically oriented 2D perovskite hetero-/homo-junctions are gently stacked, which exhibit improved self-powered characteristics. This straightforward growth strategy is an universal solution-processed method for growing 2D perovskites, laying the foundation of the 2D perovskite hetero-/homo-junction for future miniaturization and functionalization of next-generation optoelectronics.
ABSTRACT
Photodetectors are light sensors in widespread use in image sensing, optical communication, and consumer electronics. In current smart optoelectronic technology, conventional semiconductors have encountered a bottleneck caused by inflexibility and opacity. With the ever-increasing demands for versatile optoelectronic applications, perovskite-type 2D materials demonstrate great potential for advanced photodetectors inspired by molecularly thin 2D materials. Through the reduction of thickness to thin or molecularly thin levels, single-crystalline 2D perovskites can exhibit superior optoelectronic performance characteristics, such as tunable absorption property by chemical design, enhanced carrier separation by remarkable photosensing capability, and improved carrier extraction by versatile band engineering. More importantly, perovskite-type 2D materials exhibit great potential for large-scale monolithic integration to achieve all-in-one sensing-memory-computing optoelectronic devices. In this Perspective, recent progress in 2D perovskite-based photodetectors is presented in detail. The focus is on growth strategies for reducing thickness, thickness-dependent optical and electrical properties, device engineering, heterojunction fabrication, and device performance. Finally, the current challenges and future prospects in this field are presented.