A Highly Sensitive UV–vis–NIR All‐Inorganic Perovskite Quantum Dot Phototransistor Based on a Layered Heterojunction

Abstract

yields with narrow emission bandwidth, size tunable optical properties, strong optical absorption, and more impor tantly, good environmental stabilities. [1][2][3] They have also been applied to develop high performance solar cells, light emit ting diodes (LEDs) and lasers. [4][5][6][7] Several recent works [8][9][10][11] have pioneered the appli cation of IPQDs in photodetectors with vertical (photodiode) and lateral (photo conductor and photo transistor) device structures. However, most of them show low responsivity up to ≈0.64 A W −1 . The reported responsivities of IPQD devices are limited by poor carrier mobility due to the choice of interparticle ligand mate rials and high density of defect states. [12] To develop highresponsivity photodetec tors, it is vital to increase carrier diffu sion length. One approach is to decrease the density of defects and increase car rier mobility, which has been a prevalent research topic. [13] However, an alternative method to increase responsivity is to separate electrons and holes into different paths and suppress radiative recombination with the aid of layered heterojunction (LHJ). [14] This strategy should facili tate the extractions of generated carriers and thus increase the photocurrent. There are some recent works adopting this strategy and thus improving the responsivity. Zhou et al. [15] fab ricated CsPbBr 3 QD/TiO 2 compositebased photodetectors and obtained a 44fold responsivity enhancement compared to pris tine CsPbBr 3 QD photodetectors over the detection range from 350 to 550 nm. Chen et al. [16] reported hybrid phototransistors based on CsPbBr 3 QD/DTT heterojunctions and achieved the responsivity up to 1.7 × 10 4 A W −1 , however, the detection range only reached up to green wavelength on the long side. Kwak et al. [17] fabricated CsPbBr 3-x I x QD/graphene bilayer photode tectors, exhibiting a very high responsivity (≈10 8 A W −1 ) but a decent onoff ratio, the detection wavelength range is limited up to ≈650 nm. These findings encourage us to use a LHJ film in the photodetector to enhance the performance. Although such IPQDbased hybrid photodetectors exhibit high respon sivity, the detection wavelength regions are still restricted to ultravioletvisible (UV-vis) range and cannot reach near infrared (NIR) region. Furthermore, among all reported IPQD detectors, few of them are based on CsPbI 3 QDs and targeted All-inorganic perovskite quantum dots (IPQDs) are a promising material for use in various optoelectronic devices due to their excellent optoelectronic properties and high environmental stability. Here, a high-performance phototransistor based on a layered heterojunction composed of CsPbI 3 QDs and a narrow-bandgap conjugated polymer DPP-DTT is reported, which shows a high responsivity of 110 A W −1 , a specific detectivity of 2.9 × 10 13 Jones and a light to dark current ratio up to 6 × 10 3 . The heterojunction phototransistor exhibits unipolar p-type and gate bias modulated behaviors. In addition, the device exhibits a broad spectral detection range f...

Conductivity Tuning via Doping with Electron Donating and Withdrawing Molecules in Perovskite CsPbI3 Nanocrystal Films

“…The as‐prepared, undoped NC film has relatively low current for all positive gate voltages and turns on slowly at relatively large negative gate voltages, consistent with the expected characteristics of a relatively resistive p‐type material. The on–off ratio is ≈100 and extracted FET hole mobility is 1.7 × 10 −5 cm 2 V −1 s −1 , in line with a recent study on CsPbI 3 NC FETs . Upon treatment with F 4 TCNQ, the FET threshold voltage shifts positive and the on–off ratio increases, whereas BV adsorption shifts the threshold voltage to more negative voltages and decreases the on–off ratio.…”

“…Metal halide perovskite materials are now widely studied for their rediscovered, highly tunable, and desirable optoelectronic properties . Lead halide perovskites in particular have emerged as a material system of high interest for photovoltaics, lighting/display/lasing, detectors, and other applications due to a bandgap energy that is tunable throughout the visible and near infrared spectrum and the material's ability to be processed via many variable, low‐cost methods. In general, bright emission and long‐lived carriers are observed in these semiconductors despite the films often containing a large degree of structural disorder .…”

“…Additionally, a number of recent studies have explored the potential for bulk, 0D, 1D, and 2D perovskites in photodetector applications. One recent study explored perovskite NC photodetectors (via two‐terminal I – V measurements) where the NC array was the sole semiconducting material in the channel, and several recent studies have demonstrated perovskite NC phototransistors where a heterojunction between CsPbI 3 NCs and another transport material (e.g., polymer, TiO 2 , and graphene) as the primary semiconducting channel helped to overcome the poor carrier mobility in the NC layer . As such, fundamental studies are needed for understanding the ways to improve transport and photoresponse in perovskite NC FETs, photodetectors, and phototransistors.…”

Emerging Perovskite Materials with Different Nanostructures for Photodetectors

“…There are two mature methods to fabricate perovskite QDs: hotinjection and ligand-assisted reprecipitation. [23,53,54] Hot-injection method is conducted under high reaction temperature and inert atmosphere. Generally, perovskite QDs are synthesized by swiftly injecting cesium oleate into an octadecene solution containing PbX 2 , oleic acid (OA), and oleylamine (OAm) at a high temperature.…”

Lattice marginal reconstruction-enabled high ambient-tolerance perovskite quantum dot phototransistors

“…[1][2][3][4][5][6][7][8] Recently, PeQD-sensitized hybrid phototransistors have attracted considerable interest in broadband photodetection because of their higher photoresponsivity in a broader range of wavelengths than conventional photodetectors based on silicon and indium gallium arsenide. 9,10 Moreover, these three-terminal active device structures are suitable for integrated-circuit applications, such as image sensors, optical communications, and others. [11][12][13][14][15] Usually, in order to achieve PeQDs-sensitized phototransistors with excellent performance, a strong carrier coupling between the adjacent PeQDs must be accomplished.…”