There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

While the field of perovskite-based optoelectronics has mostly been dominated by photovoltaics, light-emitting diodes, and transistors, semiconducting properties peculiar to perovskites make them interesting candidates for innovative and disruptive applications in light signal detection. Perovskites combine effective light absorption in the broadband range with good photo-generation yield and high charge carrier mobility, a combination that provides promising potential for exploiting sensitive and fast photodetectors that are targeted for image sensing, optical communication, environmental monitoring or chemical/biological detection. Currently, organic–inorganic hybrid and all-inorganic halide perovskites with controlled morphologies of polycrystalline thin films, nano-particles/wires/sheets, and bulk single crystals have shown key figure-of-merit features in terms of their responsivity, detectivity, noise equivalent power, linear dynamic range, and response speed. The sensing region has been covered from ultraviolet-visible-near infrared (UV-Vis-NIR) to gamma photons based on two- or three-terminal device architectures. Diverse photoactive materials and devices with superior optoelectronic performances have stimulated attention from researchers in multidisciplinary areas. In this review, we provide a comprehensive overview of the recent progress of perovskite-based photodetectors focusing on versatile compositions, structures, and morphologies of constituent materials, and diverse device architectures toward the superior performance metrics. Combining the advantages of both organic semiconductors (facile solution processability) and inorganic semiconductors (high charge carrier mobility), perovskites are expected to replace commercial silicon for future photodetection applications.

Perovskite-based photodetectors: materials and devices

Perovskite photodetectors (PPDs), which combine the advantages of perovskite semiconductor materials with superior optical and electronic properties and solution-processed manufacturing, have emerged as a new class of revolutionary optoelectronic devices with potential for various practical applications. Encouraged by the development of various solution-synthesis and film-deposition techniques for controlling the morphology and composition of perovskite materials with interesting optoelectronic properties, increasing research attention is focused on the development of high performance PPDs. In this review, the recent progress on emerging PPDs is comprehensively summarized from the perspective of device physics and materials science. The strategies for extending the spectral response range of PPDs and improving the performance of devices are investigated. Furthermore, the methods for realizing narrowband photodetectors are also discussed, where filter-free and self-filter narrowband PPDs are achieved based on the concept of charge collection narrowing. Meanwhile, the promising future directions in this research field are proposed and discussed, including multifunctional PPDs, perovskite–organic hybrid photodetectors, flexible and transparent PPDs, self-powered PPDs, and photodetector systems and arrays. This review provides valuable insights into the current status of highly sensitive PPDs and will spur the design of new structures and devices to further enhance their photo-detection performances and meet the need of versatility in practical application.

Recent progress on highly sensitive perovskite photodetectors

Development of Organic Semiconductor Photodetectors: From Mechanism to Applications

Recent years have witnessed skyrocketing research achievements in organic-inorganic hybrid lead halide perovskites (OIHPs) in the photovoltaic field. In addition to photovoltaics, more and more studies have focused on OIHPs-based photodetectors in the past two years, due to the remarkable optoelectronic properties of OIHPs. This article summarizes the latest progress in this research field. To begin with, the factors influencing the performance of photodetectors are discussed, including both internal and external factors. In particular, the channel width and the incident power intensities should be taken into account to precisely and objectively evaluate and compare the output performance of different photodetectors. Next, photodetectors fabricated on single-component perovskites in terms of different micromorphologies are discussed, namely, 3D thin-film and single crystalline, 2D nanoplates, 1D nanowires, and 0D nanocrystals, respectively. Then, bilayer structured perovskite-based photodetectors incorporating inorganic and organic semiconductors are discussed to improve the optoelectronic performance of their pristine counterparts. Additionally, flexible OIHPs-based photodetectors are highlighted. Finally, a brief conclusion and outlook is given on the progress and challenges in the field of perovskites-based photodetectors.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201700256

Photodetectors Based on Organic-Inorganic Hybrid Lead Halide Perovskites.

Organolead halide perovskite is a newly emerging low-cost, solution-processable material with a broadband absorption from the ultraviolet (UV) to visible (Vis) region, which has attracted a great deal of interest in high-performance optoelectronic devices. However, some practicable applications need a cover of UV–Vis–NIR region for photoelectric conversion, a task that remains a significant challenge for further extending the absorption toward the near-infrared radiation (NIR) region. Here, to the best of our knowledge, we prove for the first time an ultrasensitive flexible broadband photodetector based on porous organolead perovskite-phthalocyanine heterostructure, which combines the synergetic properties of high UV–Vis absorbance of perovskite with enhanced NIR absorption for triclinic lead phthalocyanine. The photosensitivity of the as-prepared devices reaches up to 104 at a low intensity of 10 mW cm−2, which is among the largest values reported for broadband photodetectors. Significantly, performed at room temperature, the device achieves a pA scale dark current along with an ultrafast response speed of less than 0.6 ms for as-adopted full spectra. Our results provide an easy and promising route to develop low-cost, flexible and highly sensitive UV–Vis–NIR photodetectors. Energy efficient and flexible alternative photodetector that detects both visible and invisible light comes closer to real life than ever. A group of researchers from China has developed an organic-inorganic hybrid photodetector that outperforms conventional inorganic like Si and InGaAs-based photodetectors in at least two aspects: broader detection spectral range and much lower dark current. Thanks to the structural flexibility of two hybrid photosensitive materials, methyl-ammonium lead halide and lead phthalocyanine, the team engineered the large area sub-micron thick photodetector with porous structures, which is the key to reducing the standby power consumption by more than 30 times compared to the best InGaAs and Si-based photodetectors. More importantly, the hybrid photodetector needs no additional apparatus or power to cool it for continuous operation, in contrast to the InGaAs photodetector.

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Ultrasensitive flexible broadband photodetectors achieving pA scale dark current

High performance photodiode based on MoS2/pentacene heterojunction

Ultrasensitivity broadband photodetectors based on perovskite: Research on film crystallization and electrode optimization

Trap-induced current multiplication has received tremendous attention in organic photodetectors because it is not required for a pre-amplifier circuit to read weak photocurrent signals. However, a plausible correlation between energy-distinguishable trap states and device performance has not been established for guiding the device design, a task that remains a significant challenge. Here, we propose an ingenious strategy to demonstrate current multiplication by engineering an ultrathin fullerene (C-60) film as hole trap or barrier layer, which illustrates trap-state dynamics through systematical investigations on device current fluctuations in darkness and illumination conditions. The comparison of trap-dependent performances between experimental and control devices clearly shows that the traps play a critical role in generating the multiplication effect. And shallow trap states are estimated to be more favorable for improving the device restorability. Thus, we anticipate that trap engineering, by selectively passivating deep traps whilst retaining shallow ones, will be a fruitful approach for further research, leading to high-performance photodetectors with superior current multiplication and temporal response. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Ying Wang

Papers

Ultrasensitive flexible broadband photodetectors achieving pA scale dark current

High performance photodiode based on MoS2/pentacene heterojunction

Ultrasensitivity broadband photodetectors based on perovskite: Research on film crystallization and electrode optimization

Insight into trap state dynamics for exploiting current multiplication in organic photodetectors

Charge-transport interfacial modification enhanced ultraviolet (UV)/near-UV phototransistor with high sensitivity and fast response speed