Ultraviolet-Visible-Short-Wavelength Infrared Broadband and Fast-Response Photodetectors Enabled by Individual Monocrystalline Perovskite Nanoplate

Perovskite-based photodetectors exhibit potential applications in communication, neuromorphic chips, and biomedical imaging due to their outstanding photoelectric properties and facile manufacturability. However, few of perovskite-based photodetectors focus on ultraviolet-visible-short-wavelength infrared (UV–Vis–SWIR) broadband photodetection because of the relatively large bandgap. Moreover, such broadband photodetectors with individual nanocrystal channel featuring monolithic integration with functional electronic/optical components have hardly been explored. Herein, an individual monocrystalline MAPbBr₃ nanoplate-based photodetector is demonstrated that simultaneously achieves efficient UV–Vis–SWIR detection and fast-response. Nanoplate photodetectors (NPDs) are prepared by assembling single nanoplate on adjacent gold electrodes. NPDs exhibit high external quantum efficiency (EQE) and detectivity of 1200% and 5.37 × 10¹² Jones, as well as fast response with rise time of 80 µs. Notably, NPDs simultaneously achieve high EQE and fast response, exceeding most perovskite devices with multi-nanocrystal channel. Benefiting from the high specific surface area of nanoplate with surface-trap-assisted absorption, NPDs achieve high performance in the near-infrared and SWIR spectral region of 850–1450 nm. Unencapsulated devices show outstanding UV-laser-irradiation endurance and decent periodicity and repeatability after 29-day-storage in atmospheric environment. Finally, imaging applications are demonstrated. This work verifies the potential of perovskite-based broadband photodetection, and stimulates the monolithic integration of various perovskite-based devices.     

High-performance UV–vis photodetectors based on electrospun ZnO nanofiber-solution processed perovskite hybrid structures

Hybrid organic-inorganic perovskites have been demonstrated as promising candidates for broadband-responsive photodetectors.It is critical to develop perovskite-based photodetectors with excellent photodetection capability and facile fabrication processes for practical application.Herein,we designed and fabricated,for the first time,a hybrid photodetector consisting of electrospun ZnO nanofibers and perovskites.Compared to pristine ZnO or perovskite,the hybrid photodetector showed increased on-off ratio,faster response speed,and higher responsivity and detectivity.The performance of the hybrid devices was significantly enhanced by using quasi-aligned ZnO nanofiber arrays instead of disordered nanofibers,which provide efficient charge transfer between the perovskite and ZnO,shorter transmission paths,and reduced carrier loss at cross-junctions of nanofibers.Our results provide a new and promising route to integrate inorganic functional materials with perovskite for high-performance and low-cost photodetectors.     

Phase-Modulated Multidimensional Perovskites for High-Sensitivity Self-Powered UV Photodetectors

2D Ruddlesden-Popper perovskites (PVKs) have recently shown overwhelming potential in various optoelectronic devices on account of enhanced stability to their 3D counterparts. So far, regulating the phase distribution and orientation of 2D perovskite thin films remains challenging to achieve efficient charge transport. This work elucidates the balance struck between sufficient gradient sedimentation of perovskite colloids and less formation of small-n phases, which results in the layered alignment of phase compositions and thus in enhanced photoresponse. The solvent engineering strategy, together with the introduction of poly(3,4-ethylene-dioxythiophene):polystyrene sulfonate (PEDOT:PSS) and PC₇₁BM layer jointly contribute to outstanding self-powered performance of indium tin oxide/PEDOT:PSS/PVK/PC₇₁BM/Ag device, with a photocurrent of 18.4 µA and an on/off ratio up to 2800. The as-fabricated photodetector exhibits high sensitivity characteristics with the peak responsivity of 0.22 A W⁻¹ and the detectivity up to 1.3 × 10¹² Jones detected at UV-A region, outperforming most reported perovskite-based UV photodetectors and maintaining high stability over a wide spectrum ranging from UV to visible region. This discovery supplies deep insights into the control of ordered phases and crystallinity in quasi-2D perovskite films for high-performance optoelectronic devices.     

In Situ Formed Gradient Bandgap-Tunable Perovskite for Ultrahigh-Speed Color/Spectrum-Sensitive Photodetectors via Electron-Donor Control

Integration of various photodetectors with different light-sensitive materials and detection capacity is an inevitable way to achieve entire color/spectrum detection. However, the uneven capacity of each photodetector would drag the overall performance behind, especially the response speed. A response time down to nanosecond level has not previously been reported for a filter-free color/spectrum-sensitive photodetector, as far as is known. Here, a self-powered filterless color-sensitive photodetection array based on an in situ formed gradient perovskite absorber film with continuously tunable bandgap is demonstrated. Ultrahigh-speed response at nanosecond level is achieved in all the ingredient photodetectors. The junction capacitance being influenced by carrier concentration in the absorber is identified to be responsible for the detection speed. Without any optic or mechanical supporting system, the designed color detector exhibits an external quantum efficiency (EQE) up to 94% and a high spectral resolution of around 80 nm for the whole visible spectrum. This work offers a guidance to achieve fast response of perovskite-based photodetectors from the point of view of carrier-donor control and demonstrates a new avenue to establish color-sensitive photodetectors/spectrometers.     

离子液体在有机光电转换器件中的应用研究进展

近年来,离子液体因具有不易挥发、性质稳定、透光性好、导电率高、可设计性,以及易于在界面处形成双电层等物理化学性质,而展现出广阔的应用潜力和前景,逐渐成为国际科学研究的前沿和热点之一。其中,将离子液体应用于染料敏化太阳能电池(Dye-sensitized solar cells,DSSCs)、钙钛矿太阳能电池和有机光电探测器等有机光电转换器件的研究备受关注。 在有机光电转换器件中,离子液体在染料敏化太阳能电池方面的应用最为广泛且完善。高效DSSCs主要是基于有机溶剂的液态电解质结,但有机溶剂在带来较高光电转换效率的同时,其本身存在的易挥发汽化、光热稳定性差等缺点,导致DSSCs的器件寿命与长期稳定性受到影响,离子液体的引入能有效解决以上问题。此外,离子液体还以电子传输层以及界面修饰层的形式引入,具有高电荷迁移率、低功函数以及高稳定性等优点,能在一定程度上改善器件的短路电流、填充因子和光电转换效率等。因此,离子液体成为在DSSCs的实际应用中兼具性价比高、封装难度低、性能好、稳定性高四大优点的辅助材料。在钙钛矿太阳能电池方面,离子液体的低功函数和高电子迁移率以及一些特殊性质如钝化反应、黏度效应等,都能够实现对电子萃取率、电荷转移电阻、钙钛矿结晶情况等方面的控制以满足实际设计要求,进而有助于钙钛矿太阳能电池的光电转换效率、填充因子等性能指标不同程度的提升。在有机光电探测器方面,引入的离子液体能促使在与之接触的界面处形成双电层,双电层的形成及离子液体的高导电率使得入射光不必照射有机光电探测器上下电极的重叠区域仍旧可以产生较大的光电流输出,从而可以有效摆脱有机光电探测器对电极材料透光性要求的局限性。同时双电层的形成还将促进有机光电探测器工作层中的电荷分离,进一步提高有机光电探测器的响应率。 本文主要从染料敏化太阳能电池、钙钛矿太阳能电池、有机光电探测器三个方面,综述了离子液体在有机光电转换器件中的国内外应用研究进展,就离子液体对提升有机光电转换效率及其实现器件新功能的工作机理进行了详细分析,并对其未来的应用研究方向进行了展望,为今后进一步设计出更适合有机光电转换领域应用的离子液体提供参考。     

Highly Efficient and Ultrasensitive Large‐Area Flexible Photodetector Based on Perovskite Nanowires

Hybrid organic–inorganic perovskites have shown exceptional semiconducting properties and microstructural versatility for inexpensive, solution‐processable photovoltaic and optoelectronic devices. In this work, an all‐solution‐based technique in ambient environment for highly sensitive and high‐speed flexible photodetectors using high crystal quality perovskite nanowires grown on Kapton substrate is presented. At 10 V, the optimized photodetector exhibits a responsivity as high as 0.62 A W^?1, a maximum specific detectivity of 7.3 × 10¹² cm Hz^1/2 W^?1, and a rise time of 227.2 µs. It also shows remarkable photocurrent stability even beyond 5000 bending cycles. Moreover, a deposition of poly(methyl methacrylate) (PMMA) as a protective layer on the perovskite yields significantly better stability under ambient air operation: the PMMA‐protected devices are stable for over 30 days. This work demonstrates a cost‐effective fabrication technique for high‐performance flexible photodetectors and opens opportunities for research advancements in broadband and large‐scale flexible perovskite‐based optoelectronic devices.     

High Performance and Stable All‐Inorganic Metal Halide Perovskite‐Based Photodetectors for Optical Communication Applications

Photodetectors are critical parts of an optical communication system for achieving efficient photoelectronic conversion of signals, and the response speed directly determines the bandwidth of the whole system. Metal halide perovskites, an emerging class of low‐cost solution‐processed semiconductors, exhibiting strong optical absorption, low trap states, and high carrier mobility, are widely investigated in photodetection applications. Herein, through optimizing the device engineering and film quality, high‐performance photodetectors based on all‐inorganic cesium lead halide perovskite (CsPbI_xBr_3–x), which simultaneously possess high sensitivity and fast response, are demonstrated. The optimized devices processed from CsPbIBr₂ perovskite show a practically measured detectable limit of about 21.5 pW cm^?2 and a fast response time of 20 ns, which are both among the highest reported device performance of perovskite‐based photodetectors. Moreover, the photodetectors exhibit outstanding long‐term environmental stability, with negligible degradation of the photoresponse property after 2000 h under ambient conditions. In addition, the resulting perovskite photodetector is successfully integrated into an optical communication system and its applications as an optical signal receiver on transmitting text and audio signals is demonstrated. The results suggest that all‐inorganic metal halide perovskite‐based photodetectors have great application potential for optical communication.     

Perovskite crystals redissolution strategy for affordable,reproducible, efficient and stable perovskite photovoltaics

High-efficiency perovskite solar cells (PSCs) normally rely on costly, high purity (>99.99%), air-sensitive raw materials that vary batch-to-batch. The perovskite films and devices derived from conventional raw materials mixture method suffer from inferior reproducibility of optoelectronic properties and performance, as well as discounted promise towards low-cost scalable manufacturing. Distinguished from the direct mixing of raw materials, the preparation of perovskite films with precursors made by the redissolution of perovskite crystals holds the promise to make PSCs more affordable, reproducible, efficient and stable. The resultant perovskite films inherit the exceptional characteristics of the parent perovskite crystals, such as high crystallinity, high purity, accurate stoichiometric ratio, and low trap-state density, as well as good ambient and phase stability. Herein, we summarize recent progress on the employment of the perovskite crystals redissolution strategy for achieving low-cost, efficient perovskite-based solar-to-electricity conversion, which will help both popularize the redissolution strategy and reveal unprecedented advantages gained by its adoption.     

Nested Inverse Opal Perovskite toward Superior Flexible and Self-Powered Photodetection Performance

Flexible and self-powered perovskite photodetectors have attracted tremendous research interests due to their applications in wearable and portable devices. However, the conventional planar structured photodetectors are always accompanied with limited device performance and undesired mechanical stability. Herein, a nested inverse opal (NIO) structured perovskite photodetector via a facile template-assisted spin-coating method is reported. The coupling effect of enhanced light capture, increased carrier transport, and improved perovskite film quality enables NIO device to exhibit superior photoresponse performance. The NIO photodetector exhibits a high responsivity of 473 mA W⁻¹ and detectivity up to 1.35 × 10¹³ Jones at 720 nm without external bias. The NIO structure can efficiently release mechanical stress during the bending process and the photocurrent has no degradation even after 500 cycles of bending. Moreover, the unencapsulated NIO device can operate for over 16 d under ambient conditions, presenting a significantly enhanced environmental stability compared to the planar device. This work demonstrates that deliberate structural design is an effective avenue for constructing self-powered, flexible, and stable optoelectronic devices.     

Self‐Powered,Flexible, and Solution‐Processable Perovskite Photodetector Based on Low‐Cost Carbon Cloth

Flexible perovskite photodetectors are usually constructed on indium‐tin‐oxide‐coated polymer substrates, which are expensive, fragile, and not resistant to high temperature. Herein, for the first time, a high‐performance flexible perovskite photodetector is fabricated based on low‐cost carbon cloth via a facile solution processable strategy. In this device, perovskite microcrystal and Spiro‐OMeTAD (hole transporting material) blended film act as active materials for light detection, and carbon cloth serves as both a flexible substrate and a conductive electrode. The as‐fabricated photodetector shows a broad spectrum response from ultraviolet to near‐infrared light, high responsivity, fast response speed, long‐term stability, and self‐powered capability. Flexible devices show negligible degradation after several tens of bending cycles and at the extremely bending angle of 180°. This work promises a new technique to construct flexible, high‐performance photodetectors with low cost and self‐powered capability.     

A Light Harvesting,Self‐Powered Monolith Tactile Sensor Based on Electric Field Induced Effects in MAPbI3 Perovskite

Organolead trihalide perovskite MAPbI₃ shows a distinctive combination of properties such as being ferroelectric and semiconducting, with ion migration effects under poling by electric fields. The combination of its ferroelectric and semiconducting nature is used to make a light harvesting, self‐powered tactile sensor. This sensor interfaces ZnO nanosheets as a pressure‐sensitive drain on the MAPbI₃ film and once poled is operational for at least 72 h with just light illumination. The sensor is monolithic in structure, has linear response till 76 kPa, and is able to operate continuously as the energy harvesting mechanism is decoupled from its pressure sensing mechanism. It has a sensitivity of 0.57 kPa^?1, which can be modulated by the strength of the poling field. The understanding of these effects in perovskite materials and their application in power source free devices are of significance to a wide array of fields where these materials are being researched and applied.     

Piezo-phototronic effect enhanced polarization-sensitive photodetectors based on cation-mixed organic–inorganic perovskite nanowires

Piezo-phototronic effect has been extensively investigated for the third generation semiconductor nanowires. Here, we present a demonstration that piezo-phototronic effect can even be applied to tune polarization-sensitive photodetectors based on cation-mixed organic–inorganic perovskite nanowires. A big anisotropic photoluminescence (PL) with linearly polarized light-excitation was found due to a strong spontaneous piezoelectric polarization besides the anisotropic crystal structure and morphology. The piezo-phototronic effect was utilized to tune the PL intensity, and an improved anisotropic PL ratio from 9.36 to 10.21 for linearly polarized light-excitation was obtained thanks to the modulation by piezo-potential. And a circularly polarization-sensitive PL characterized with circular dichroism ratio was also discovered, which was found to be modulated from 0.085 to 0.555 (with a 5.5-fold improvement) within the range of applied strain. The circular dichroism was resulted from the joint effects of the modulated Rashba spin–orbit coupling and the asymmetric carriers separation and recombination for right- and left-handed helicity due to the presence of effective piezo-potential. These findings not only reveal the promising optoelectronic applications of piezo-phototronic effect in perovskite-based polarization-sensitive photodetectors, but also illuminate fundamental understandings of their polarization properties of perovskite nanowires.     

Perovskite–Erbium Silicate Nanosheet Hybrid Waveguide Photodetectors at the Near‐Infrared Telecommunication Band

Methylammonium lead halide perovskites have attracted enormous attentions due to their superior optical and electronic properties. However, the photodetection at near‐infrared telecommunication wavelengths is hardly achievable because of their wide bandgaps. Here, this study demonstrates, for the first time, novel perovskite–erbium silicate nanosheet hybrid photodetectors with remarkable spectral response at ≈1.54 µm. Under the near‐infrared light illumination, the erbium silicate nanosheets can give strong upconversion luminescence, which will be well confined in their cavities and then be efficiently coupled into and simultaneously excite the adjacent perovskite to realize photodetection. These devices own prominent responsivity and external quantum efficiency as high as previously reported microscale silicon‐based subbandgap photodetectors. More importantly, the photoresponse speed (≈900 µs) is faster by five orders than the ever reported hot electron silicon‐based photodetectors at telecommunication wavelengths. The realization of perovskite‐based telecommunication band photodetectors will open new chances for applications in advanced integrated photonics devices and systems.     

High‐Performance Single‐Crystalline Perovskite Thin‐Film Photodetector

The best performing modern optoelectronic devices rely on single‐crystalline thin‐film (SC‐TF) semiconductors grown epitaxially. The emerging halide perovskites, which can be synthesized via low‐cost solution‐based methods, have achieved substantial success in various optoelectronic devices including solar cells, lasers, light‐emitting diodes, and photodetectors. However, to date, the performance of these perovskite devices based on polycrystalline thin‐film active layers lags behind the epitaxially grown semiconductor devices. Here, a photodetector based on SC‐TF perovskite active layer is reported with a record performance of a 50 million gain, 70 GHz gain‐bandwidth product, and a 100‐photon level detection limit at 180 Hz modulation bandwidth, which as far as we know are the highest values among all the reported perovskite photodetectors. The superior performance of the device originates from replacing polycrystalline thin film by a thickness‐optimized SC‐TF with much higher mobility and longer recombination time. The results indicate that high‐performance perovskite devices based on SC‐TF may become competitive in modern optoelectronics.     

High‐Gain 200 ns Photodetectors from Self‐Aligned CdS–CdSe Core–Shell Nanowalls

1D core–shell heterojunction nanostructures have great potential for high‐performance, compact optoelectronic devices owing to their high interface area to volume ratio, yet their bottom‐up assembly toward scalable fabrication remains a challenge. Here the site‐controlled growth of aligned CdS–CdSe core–shell nanowalls is reported by a combination of surface‐guided vapor–liquid–solid horizontal growth and selective‐area vapor–solid epitaxial growth, and their integration into photodetectors at wafer‐scale without postgrowth transfer, alignment, or selective shell‐etching steps. The photocurrent response of these nanowalls is reduced to 200 ns with a gain of up to 3.8 × 10³ and a photoresponsivity of 1.2 × 10³ A W^?1, the fastest response at such a high gain ever reported for photodetectors based on compound semiconductor nanostructures. The simultaneous achievement of sub‐microsecond response and high‐gain photocurrent is attributed to the virtues of both the epitaxial CdS–CdSe heterojunction and the enhanced charge‐separation efficiency of the core–shell nanowall geometry. Surface‐guided nanostructures are promising templates for wafer‐scale fabrication of self‐aligned core–shell nanostructures toward scalable fabrication of high‐performance compact photodetectors from the bottom‐up.     

Hybrid Organic–Inorganic Perovskite Photodetectors

Hybrid organic–inorganic perovskite materials garner enormous attention for a wide range of optoelectronic devices. Due to their attractive optical and electrical properties including high optical absorption coefficient, high carrier mobility, and long carrier diffusion length, perovskites have opened up a great opportunity for high performance photodetectors. This review aims to give a comprehensive summary of the significant results on perovskite‐based photodetectors, focusing on the relationship among the perovskite structures, device configurations, and photodetecting performances. An introduction of recent progress in various perovskite structure‐based photodetectors is provided. The emphasis is placed on the correlation between the perovskite structure and the device performance. Next, recent developments of bandgap‐tunable perovskite and hybrid photodetectors built from perovskite heterostructures are highlighted. Then, effective approaches to enhance the stability of perovskite photodetector are presented, followed by the introduction of flexible and self‐powered perovskite photodetectors. Finally, a summary of the previous results is given, and the major challenges that need to be addressed in the future are outlined. A comprehensive summary of the research status on perovskite photodetectors is hoped to push forward the development of this field.     

Perovskite Single-Crystal Microwire-Array Photodetectors with Performance Stability beyond 1 Year

Compared with thin-film morphology, 1D perovskite structures such as micro/nanowires with fewer grain boundaries and lower defect density are very suitable for high-performance photodetectors with higher stability. Although the stability of perovskite microwire-based photodetectors has been substantially enhanced in comparison with that of photodetectors based on thin-film morphology, practical applications require further improvements to the stability before implementation. In this study, a template-assisted method is developed to prepare methylammonium lead bromide (MAPbBr₃) micro/nanowire structures, which are encapsulated in situ by a protective hydrophobic molecular layer. The combination of the protective layer, high crystalline quality, and highly ordered microstructures significantly improve the stability of the MAPbBr₃ single-crystal microwire arrays. Consequently, these MAPbBr₃ single-crystal microwire-array-based photodetectors exhibit significant long-term stability, maintaining 96% of the initial photocurrent after 1 year without further encapsulation. The lifetime of such photodetectors is hence approximately four times longer than that of the most stable previously reported perovskite micro/nanowire-based photodetector; this is thought to be the most stable perovskite photodetector reported thus far. Furthermore, this work should contribute further toward the realization of perovskite 1D structures with long-term stability.     

Extending the Photovoltaic Response of Perovskite Solar Cells into the Near‐Infrared with a Narrow‐Bandgap Organic Semiconductor

Typical lead‐based perovskites solar cells show an onset of photogeneration around 800 nm, leaving plenty of spectral loss in the near‐infrared (NIR). Extending light absorption beyond 800 nm into the NIR should increase photocurrent generation and further improve photovoltaic efficiency of perovskite solar cells (PSCs). Here, a simple and facile approach is reported to incorporate a NIR‐chromophore that is also a Lewis‐base into perovskite absorbers to broaden their photoresponse and increase their photovoltaic efficiency. Compared with pristine PSCs without such an organic chromophore, these solar cells generate photocurrent in the NIR beyond the band edge of the perovskite active layer alone. Given the Lewis‐basic nature of the organic semiconductor, its addition to the photoactive layer also effectively passivates perovskite defects. These films thus exhibit significantly reduced trap densities, enhanced hole and electron mobilities, and suppressed illumination‐induced ion migration. As a consequence, perovskite solar cells with organic chromophore exhibit an enhanced efficiency of 21.6%, and substantively improved operational stability under continuous one‐sun illumination. The results demonstrate the potential generalizability of directly incorporating a multifunctional organic semiconductor that both extends light absorption and passivates surface traps in perovskite active layers to yield highly efficient and stable NIR‐harvesting PSCs.     

Tailoring the Performances of Lead Halide Perovskite Devices with Electron‐Beam Irradiation

Lead halide perovskites are intensively studied in past few years due to their potential applications in optoelectronic devices such as solar cells, photodetectors, light‐emitting diodes (LED), and lasers. In addition to the rapid developments in material synthesis and device fabrication, it is also very interesting to postsynthetically control the optical properties with external irradiations. Here, the influences of very low energy (10–20 keV) electron beam of standard electron beam lithography are experimentally explored on the properties of lead halide perovskites. It is confirmed that the radiolysis process also happens and it can selectively change the photoluminescence, enabling the direct formation of nanolaser array, microsized light emitter array, and micropictures with an electron beam writer. Interestingly, it is found that discontinuous metallic lead layers are formed on the top and bottom surfaces of perovskite microplate during the radiolysis process, which can act as carrier conducting layers and significantly increase the photocurrent of perovskite photodetector by a factor of 217%. By using the electron beam with low energy to modify the perovskite, this method promises to shape the emission patterns for micro‐LED with well‐preserved optical properties and improves the photocurrent of photodetector.     

Halide Perovskites for Nonlinear Optics

Halide perovskites provide an ideal platform for engineering highly promising semiconductor materials for a wide range of applications in optoelectronic devices, such as photovoltaics, light-emitting diodes, photodetectors, and lasers. More recently, increasing research efforts have been directed toward the nonlinear optical properties of halide perovskites because of their unique chemical and electronic properties, which are of crucial importance for advancing their applications in next-generation photonic devices. Here, the current state of the art in the field of nonlinear optics (NLO) in halide perovskite materials is reviewed. Halide perovskites are categorized into hybrid organic/inorganic and pure inorganic ones, and their second-, third-, and higher-order NLO properties are summarized. The performance of halide perovskite materials in NLO devices such as upconversion lasers and ultrafast laser modulators is analyzed. Several potential perspectives and research directions of these promising materials for nonlinear optics are presented.