Hybrid Phototransistor Research Articles

Multi‐Wavelength Optoelectronic Synaptic Transistors Based on Transition Metal Telluride‐Sulfide Heterostructures

AbstractNeuromorphic visual systems based on optogenetic techniques have colossal potential for in‐memory computing with prospects of developing artificial intelligence vision systems. However, conventional transistor architectures face formidable challenges in efficient signal processing owing to limitations in the intrinsic properties of active channel materials. In this work, a novel transition metal telluride‐sulfide hybrid heterojunction‐based optoelectronic synaptic phototransistor is proposed, in which UV–vis responsive zinc oxide encapsulated few‐layer tungsten disulfide channel is decorated with near‐infrared sensitive 0D cobalt ditelluride (CoTe2) nanocrystals (NCs), eliciting the ability to sense, store, and process optical signals across a broad range of the electromagnetic spectrum. This meticulously designed three‐layered heterostructure, based on their interfacial band alignments, enables high photoresponsivity up to ≈2.6 × 103 A W−1 at a back‐gate bias of 20 V, leading to the brain‐inspired synaptic applications with an average power consumption as low as 75 pJ for each training process. The device exhibits excitatory postsynaptic current, paired‐pulse facilitation with an index above 150%, as well as light‐modulated synaptic plasticity by mimicking biological synapses, which mainly originate from trapped holes in Co‐vacancy mediated surface defect states of CoTe2 NCs. Hence, this 2D material‐based hybrid phototransistor appears to be a promising candidate for energy‐efficient next‐generation brain‐inspired neuromorphic vision systems.

IGZO Phototransistor with Ultrahigh Sensitivity at Broad Spectrum Range (450–950 nm) Realized by Incorporating PM6:Y6 Bulk Heterojunction

AbstractAmong various photoresponsive materials, organic materials have gained interest due to their low cost, large‐scale yields, and compatibility with flexible substrates. However, their low photoresponsivity compared to inorganic counterparts has been consistently pointed out as a limitation. To address this issue, a highly photoresponsive PM6:Y6/IGZO hybrid phototransistor is presented with a broad spectral range of 450–950 nm. The photoresponse of the device is enhanced by controlling the PM6:Y6 blending ratio, active layer thickness, and solvent additive treatment. The PM6:Y6 blending ratio and thickness are optimized to promote charge separation and efficient charge transport, leading to a significant increase in photoresponsivity. Moreover, solvent additives are employed to improve the crystallinity of the PM6:Y6 film, which further enhanced the charge transport. As a result, the PM6:Y6/IGZO hybrid phototransistor exhibited exceptional performance, with an ultrahigh photoresponsivity of 2.2 × 108 A W−1 and specific detectivity of 9.8 × 1016 Jones under 750 nm light with an intensity of only 1.03 nW cm−2. These results highlight the potential of organic materials in developing high‐performance phototransistors.

High-sensitivity hybrid MoSe2/AgInGaS quantum dot heterojunction photodetector.

Zero-dimensional (0D)-two-dimensional (2D) hybrid photodetectors have received widespread attention due to their outstanding photoelectric performances. However, these devices with high performances mainly employ quantum dots that contain toxic elements as sensitizing layers, which restricts their practical applications. In this work, we used eco-friendly AgInGaS quantum dots (AIGS-QDs) as a highly light-absorbing layer and molybdenum diselenide (MoSe2) as a charge transfer layer to construct a 0D-2D hybrid photodetector. Notably, we observed that MoSe2 strongly quenches the photoluminescence (PL) of AIGS-QDs and decreases the decay time of PL in the MoSe2/AIGS-QDs heterojunction. The MoSe2/AIGS-QDs hybrid photodetector demonstrates a responsivity of 14.3 A W-1 and a high detectivity of 6.4 × 1011 Jones. Moreover, the detectivity of the hybrid phototransistor is significantly enhanced by more than three times compared with that of the MoSe2 photodetector. Our work suggests that 0D-2D hybrid photodetectors with multiplex I-III-VI QDs provide promising potential for future high-sensitivity photodetectors.

Organic optoelectrical synaptic transistors for color information processing

The light-induced synaptic transistors, with their large-scale and cost-effective benefits, hold significant promise for advancing neuromorphic electronics. In this work, we propose a hybrid phototransistor with a channel layer composed of C8-BTBT and PM6. This device exhibits an extended optical response range in comparison to pure C8-BTBT transistors. In addition, the device shows excellent synaptic plasticity under red, green, and blue light stimuli, with the potential for tuning through light dosage and pulse duration. The study further confirms consistent device performance and reliable operation. Moreover, we show that this type of device can be fabricated into array to write the letters “C”, “S”, and “U” and store red, green, and blue information. These experimental results show the excellent responsiveness and storage performance of our devices under red, green, and blue light stimuli, suggesting promising applications in artificial vision.

Gate Voltage Adjusting PbS‐I Quantum‐Dot‐Sensitized InGaZnO Hybrid Phototransistor with High‐Sensitivity

AbstractPbS QDs/a‐IGZO based sensitized photo field‐effect transistors are promising candidate for next‐generation near‐infrared photodetectors due to their ultra‐high sensitivity, gate tunability, and ease of integration. However, the reported PbS QDs/a‐IGZO based devices are all dependent on the solid‐state ligand exchange, and are troubled by problems such as poor repeatability, poor air stability, and negative influence on the transfer characteristic curve. In this article, for the first time, optimized high‐quality PbI2 capped PbS QDs films prepared by the solution‐phase ligand exchange are applied to PbS QDs/a‐IGZO sensitized Photo‐FETs. The device not only gets rid of the tedious layer‐by‐layer deposition, but also exhibits a detectivity of 9.3 × 1012 Jones, a responsivity of 45.3 A W−1 and a decay time of 24.6 ms (@1064 nm, 1.89 mW cm−2). The operation mode of the sensitized device can meet different detection requirements by adjusting gate voltage. Importantly, the responsivity of the unencapsulated PbS‐I based device remained unchanged after six months air exposure, demonstrating excellent air stability.

Ultrasensitive Near-Infrared InAs Colloidal Quantum Dot-ZnON Hybrid Phototransistor Based on a Gradated Band Structure.

Amorphous metal oxide semiconductor phototransistors (MOTPs) integrated with colloidal quantum dots (QDs) (QD-MOTPs) are promising infrared photodetectors owing to their high photoconductive gain, low off-current level, and high compatibility with pixel circuits. However, to date, the poor mobility of conventional MOTPs, such as indium gallium zinc oxide (IGZO), and the toxicity of lead (Pb)-based QDs, such as lead sulfide and lead selenide, has limited the commercial applications of QD-MOTPs. Herein, an ultrasensitive QD-MOTP fabricated by integrating a high-mobility zinc oxynitride (ZnON)-based MOTP and lead-free indium arsenide (InAs) QDs is demonstrated. A new gradated bandgap structure is introduced in the InAs QD layer that absorbs infrared light, which prevents carriers from moving backward and effectively reduces electron-hole recombination. Chemical, optical, and structural analyses confirm the movement of the photoexcited carriers in the graded band structure. The novel QD-MOTP exhibits an outstanding performance with a responsivity of 1.15 × 105 A W-1 and detectivity of 5.32 × 1016 Jones at a light power density of 2 µW cm-2 under illumination at 905nm.

Ligand-induced charge transport modulation and enhanced photoresponse in hybrid MoS2/quantum dot phototransistors

Mix-dimensional heterostructures of colloidal quantum dots (QDs) and two-dimensional (2D) layered materials have attracted growing interest in photodetection due to the combination of high optical absorption and superior charge transport characteristic. However, the QD sensitizing layer usually introduces uncontrolled doping to the 2D materials originating from the capping ligands, which deteriorates the gate modulation capability and interfacial charge transfer efficiency. In this work, we demonstrated that the photoresponse of MoS2/QD hybrid phototransistor was greatly enhanced by selecting ligand treatment strategy. The carrier concentration and mobility in MoS2 could be effectively tuned via surface doping of 3-mercaptopropionic acid ligand, resulting in high on–off current ratio and low dark current of around 10 pA. The signal-to-noise ratio was improved by three orders of magnitude compared to the pristine MoS2 devices, indicating a dramatically enhanced photoresponse sensitivity. The specific detectivity reached 3.1 × 1013 Jones at the illumination power of 2.3 mW/cm2. The photoresponse speed of the hybrid device was enhanced by about 100 times, owing to the effective interfacial charge transfer which was revealed by the photoluminescence quenching and optoelectrical characterizations. Our work may push a new path to design the interface of mix-dimensional heterostructure and develop high-performance electronic and optoelectronic devices.

Boosting the Sensitivity of WSe2 Phototransistor via Janus Interfaces with 2D Perovskite and Ferroelectric Layers

Hybrid systems have recently attracted increasing attention, which combine the special attributes of each constitute and create interesting functionalities through multiple heterointerface interactions. Here, we design a two-dimensional (2D) hybrid phototransistor utilizing Janus-interface engineering, in which the WSe2 channel combines light-sensitive perovskite and spontaneously polarized ferroelectrics, achieving collective ultrasensitive detection performance. The top perovskite (BA2(MA)3Pb4I13) layer can absorb the light efficiently and provide generous photoexcited holes to WSe2. WSe2 exhibit p-type semiconducting states of different degrees due to the selective light-operated doping effect, which also enables the ultrahigh photocurrent of the device. The bottom ferroelectric (Hf0.5Zr0.5O2) layer dramatically decreases the dark current, which should be attributed to the ferroelectric polarization assisted charge trapping effect and improved gate control. As a whole, our phototransistors show excellent photoelectric performances across the ultraviolet to near-infrared range (360-1050 nm), including an ultrahigh ON/OFF current ratio > 109 and low noise-equivalent power of 1.3 fW/Hz1/2, all of which are highly competitive in 2D semiconductor-based optoelectronic devices. In particular, the devices show excellent weak light detection ability, where the distinguishable photoswitching signal is obtained even under a record-low light intensity down to 1.6 nW/cm2, while showing a high responsivity of 2.3 × 105 A/W and a specific detectivity of 4.1 × 1014 Jones. Our work demonstrates that Janus-interface design makes the upper and lower interfaces complement each other for the joint advancement into high-performance optoelectronic applications, providing a picture to realize the integrated engineering on carrier dynamics by light irradiation, electric field, interfacial trapping, and band alignment.

High-Performance Broad-Band Photodetection Based on Graphene-MoS2xSe2(1-x) Alloy Engineered Phototransistors.

The concept of alloy engineering has emerged as a viable technique toward tuning the band gap as well as engineering the defect levels in two-dimensional transition-metal dichalcognides (TMDCs). The possibility of synthesizing these ultrathin TMDC materials through a chemical route has opened up realistic possibilities to fabricate hybrid multifunctional devices. By synthesizing nanosheets with different composites of MoS2xSe2(1-x) (x = 0 - 1) using simple chemical methods, we systematically investigate the photoresponse properties of three terminal hybrid devices by decorating large-area graphene with these nanosheets (x = 0, 0.5, 1) in 2D-2D configurations. Among them, the graphene-MoSSe hybrid phototransistor exhibits optoelectronic properties superior to those of its binary counterparts. The device exhibits extremely high photoresponsivity (>104 A/W), low noise equivalent power (∼10-14 W/Hz0.5), and higher specific detectivity (∼1011 jones) in the wide UV-NIR (365-810 nm) range with excellent gate tunability. The broad-band light absorption of MoSSe, ultrafast charge transport in graphene, and controllable defect engineering in MoSSe makes this device extremely attractive. Our work demonstrates the large-area scalability with the wafer-scale production of MoS2xSe2(1-x) alloys, having important implications toward the facile and scalable fabrication of high-performance optoelectronic devices and providing important insights into the fundamental interactions between van der Waals materials.

Enhanced performance and stability in InGaZnO NIR phototransistors with alumina-infilled quantum dot solid

The optimized ALD infilling process for depositing Al2O3 in the vertical direction of PbS QDs enhances the photoresponsivity, relaxation rate and the air stability of PbS QDs hybrid IGZO NIR phototransistors. Infilled Al2O3, which is gradually deposited from the top of PbS QDs to the PbS/IGZO interface (1) passivates the trap sites up to the interface of PbS/IGZO without disturbing charge transfer and (2) prevents QDs deterioration caused by outside air. Therefore, an Al2O3 infilled PbS QD/IGZO hybrid phototransistor (AI-PTs) exhibited enhanced photoresponsivity from 96.4 A/W to 1.65 × 102 A/W and a relaxation time decrease from 0.52 to 0.03 s under NIR light (880 nm) compared to hybrid phototransistors without Al2O3 (RF-PTs). In addition, AI-PTs also showed improved shelf stability over 4 months compared to RF-PTs. Finally, all devices we manufactured have the potential to be manufactured in an array, and this ALD technique is a means of fabricating robust QDs/metal oxide hybrids for optoelectronic devices.

Inorganic-Organic Hybrid Phototransistor Array with Enhanced Photogating Effect for Dynamic Near-Infrared Light Sensing and Image Preprocessing.

Narrow-band-gap organic semiconductors have emerged as appealing near-infrared (NIR) sensing materials by virtue of their unique optoelectronic properties. However, their limited carrier mobility impedes the implementation of large-area, dynamic NIR sensor arrays. In this work, high-performance inorganic-organic hybrid phototransistor arrays are achieved for NIR sensing, by taking advantage of the high electron mobility of In2O3 and the strong NIR absorption of a BTPV-4F:PTB7-Th bulk heterojunction (BHJ) with an enhanced photogating effect. As a result, the hybrid phototransistors reach a high responsivity of 1393.0 A W-1, a high specific detectivity of 4.8 × 1012 jones, and a fast response of 0.72 ms to NIR light (900 nm). Meanwhile, an integrated 16 × 16 phototransistor array with a one-transistor-one-phototransistor (1T1PT) architecture is achieved. On the basis of the enhanced photogating effect, the phototransistor array can not only achieve real-time, dynamic NIR light mapping but also implement image preprocessing, which is promising for advanced NIR image sensors.

High-performance hybrid graphene-CsPbBr3 perovskite nanocrystals phototransistor

Integrating graphene with other highly light absorptive materials into heterostructures is of great interest to improve the optoelectronic properties of graphene based phototransistors. Here, we fabricated a hybrid graphene-CsPbBr3 nanocrystal (NCs) phototransistor using CsPbBr3 NCs with large absorption coefficient as light absorption materials and graphene with high mobility as charge transport layer. The graphene-CsPbBr3 NCs phototransistor showed high photo response performances with responsivity (R) of 0.54 A/W at the incident light irradiation (Ee) of 56 mW/cm2. Moreover, the phototransistor exhibited rapid photo response with rise/decay time of 38/58 ms. The hybrid phototransistor has great potential applications in the photodetection and multifunction optoelectronics.

Mixed-Halide Perovskite Film-Based Neuromorphic Phototransistors for Mimicking Experience-History-Dependent Sensory Adaptation.

Sensory adaptation is an essential function for humans to live on the earth. Herein, a hybrid synaptic phototransistor based on the mixed-halide perovskite/organic semiconductor film is reported. This hybrid phototransistor achieves photosensitive performance including a high photoresponsivity over 4 × 103 A/W and an excellent specific detectivity of 2.8 × 1016 Jones. Due to the photoinduced halide-ion segregation of the mixed-halide perovskites and their slow recovery properties, the experience-history-dependent sensory adaptation behavior can be mimicked. Moreover, the light pulse width, intensity, light wavelength, and gate bias can be used to regulate the adaptation processes to improve its adaptability and perceptibility in different environments. The CsPbBrxI3-x/organic semiconductor hybrid films produced by spin coating are beneficial to large-scale fabrication. This study fabricates a novel solution-processable light-stimulated synapse based on inorganic perovskites for mimicking the human sensory adaptation that makes it possible to approach artificial neural sensory systems.

Flexible and Air‐Stable Near‐Infrared Sensors Based on Solution‐Processed Inorganic–Organic Hybrid Phototransistors

AbstractFlexible and air‐stable phototransistors are highly demanded for wearable near‐infrared (NIR) image sensors. However, advanced NIR sensors via low‐cost, solution‐based processes remained a challenge. Herein, high‐performance inorganic–organic hybrid phototransistors are achieved based on solution processed n‐type metal oxide/polymer semiconductor heterostructures of In2O3/poly{5,5′‐bis[3,5‐bis(thienyl)phenyl]‐2,2′‐bithiophene‐3‐ethylesterthiophene]} (PTPBT‐ET). The In2O3/PTPBT‐ET hybrid phototransistor combines the advantages of both fast electron transport in In2O3 and high photoresponse in PTPBT‐ET, showing high saturation mobility of 7.1 cm2 V−1 s−1 and large current on/off ratio of >107. As a result, the phototransistor exhibits high performance towards NIR light sensing with a responsivity of 200 A W−1, a specific detectivity of 1.2 × 1013 Jones, and fast photoresponse with rise/fall time of 5/120 ms. Remarkably, the hybrid phototransistor, without any passivation, demonstrates excellent electrical stability without performance degradation even after 160 days in air. A 10 × 10 phototransistor array is also enabled by virtue of the high device uniformity. Lastly, flexible In2O3/PTPBT‐ET phototransistor on polyimide substrate is attained, exhibiting outstanding mechanical flexibility up to 1000 bending/releasing cycles at a bending radius of 5 mm. These achievements pave the way for constructing air‐stable hybrid phototransistors for flexible NIR image sensor applications.

Enhanced Electro-Optical Performance of Inorganic Perovskite/a-InGaZnO Phototransistors Enabled by Sn-Pb Binary Incorporation with a Selective Photonic Deactivation.

Optoelectronic applications using perovskites have emerged as one of the most promising platforms such as phototransistors, photovoltaics, and photodetectors. However, high-performance and reliable perovskite photonic devices are often hindered by the limited spectral ranges of the perovskite system along with the lack of appropriate processing technologies for the implementation of reliable device architectures. Here, we explore a hybrid phototransistor with a heterojunction of a Sn-Pb binary mixed halide perovskite (CsSn0.6Pb0.4I2.6Br0.4) light absorber and an amorphous-In-Ga-Zn-O (a-IGZO) charge carrying layer. By incorporating Sn-Pb binary components with an all-inorganic base, broadening of light-absorbing spectral ranges with enhanced stability has been achieved, indicating inevitable highly increased conductivity, which triggers a high off-current of the devices. Accordingly, the selectively ultraviolet (UV)-irradiated electrical deactivation (SUED) process is carried out to suppress the high off-current with a reliable device structure. Particularly, it is noted that the selective UV irradiation can facilitate oxidation and distortion of the chemical structure in specific perovskite regions, providing enhanced gate bias modulation of the phototransistor with an increased on/off-current ratio from ∼103 to ∼106. Finally, the SUED-processed phototransistor exhibits an improvement in the photosensitivity by more than 3 orders of magnitude up to 8.0 × 104 and detects in the spectral range from visible to near-infrared (NIR) light (∼860 nm) with good on/off switching behaviors.

High‐Performance Quasi‐2D Perovskite/Single‐Walled Carbon Nanotube Phototransistors for Low‐Cost and Sensitive Broadband Photodetection

Quasi‐2D Ruddlesden–Popper perovskites (RPPs) have emerged as promising functional materials for optoelectronics due to the highly tunable optoelectronic properties and have been considered as alternative candidates for semiconductors in photodetectors. However, RPPs normally show low carrier mobilities, which is unfavorable for the performance of photodetectors. Herein, a solution‐processed hybrid phototransistor based on RPP/single‐walled carbon nanotube (SWCNT) heterostructure is reported. A vertical composition gradient is formed upon RPP film preparation, which leads to a gradient type‐II heterojunction in the film. More importantly, the high carrier mobility of SWCNTs can result in ultrahigh responsivity and detectivity of 2 × 106 A W−1 and 7 × 1014 Jones, respectively. In addition, high on/off ratio of ≈103 can be achieved in the phototransistors. Herein, the high potential of RPP/SWCNT hybrid phototransistors as next‐generation photodetectors with superior sensitivity is demonstrated.

InZnON-based Thin Film Transistor for the Development of New Type Photo Detec-tors with a Colloidal Quantum Dots Sensitive Layer

Some applications of thin film transistors (TFTs) need the bottom-gate architecture and unpassivated channel backside. In present work, we propose rather simple way to fabricate nitrogen doped InZnO-based TFT by DC reactive magnetron sputtering technique. The moderate nitrogen doping of the channel's semiconductor layer is studied in terms of the reproducibility and stability device's electrical characteristics. When nitrogen concentration in gas mix reaches the upper level of 71 % the best TFT parameters are achieved such as VON = -0.3 V, μ = 12 cm2/Vs, SS = 0.5 V/dec. The TFTs operate in depletion mode exhibiting high turn on/turn off current ratio more than 106. It is shown that the oxidative post-fabrication annealing at 250 °C in pure oxygen and next ageing in dry air for several hours provide highly stable operational characteristics under negative and positive bias stresses despite open channel backside. The prospects of using the thin-film transistor for the new type of photo detectors with a colloidal quantum dots (CQDs) sensitive layer are demonstrated. The solution-cast colloidal-quantum-dots were decorated on the nitrogen doped InZnO layer by spin-coating method. N-type CdSe/ZnS CQDs modified by the ligand (pyridine) are utilized as electron donor to inject electron to the channel layer. Higher photocurrent responsibility about 104 A/W at incident monochromatic light 405 nm is reached for hybrid phototransistor.

Solution Processed Hybrid Polymer: HgTe Quantum Dot Phototransistor with High Sensitivity and Fast Infrared Response up to 2400nm at Room Temperature.

Narrow bandgap semiconductor‐based photodetectors often suffer from high room‐temperature noise and are therefore operated at low temperatures. Here, a hybrid poly(3‐hexylthiophene) (P3HT): HgTe quantum dot (QD) phototransistor is reported, which exhibits high sensitivity and fast photodetection up to 2400 nm wavelength range at room temperature. The active layer of the phototransistor consists of HgTe QDs well dispersed in a P3HT matrix. Fourier‐transform infrared spectra confirm that chemical grafting between P3HT and HgTe QDs is realized after undergoing prolonged coblend stirring and a ligand exchange process. Thanks to the shifting of the charge transport into the P3HT and the partial passivation of the surface traps of HgTe QDs in the blend, the P3HT: HgTe QD hybrid phototransistor shows significantly improved gate‐voltage tuning, 15 times faster response, and ≈80% reduction in the noise level compared to a pristine HgTe QD control device. More than 1011 Jones specific detectivity (estimated from the noise spectral density measured at 1 kHz) is achieved at room temperature, and the response time (measured at 22 mW cm−2 illumination intensity) of the device is less than 1.5 µs. That is comparable to commercial epitaxially grown IR photodetectors operated in the same wavelength range.

Gate stimulated high-performance MoS2-In(OH)xSe phototransistor

Two-dimensional (2D) materials such as graphene and MoS2 have shown great potential in photodetection platforms. Photoresponsivity and photoresponse speed are two important parameters illustrating photodetector performances. Although various hybrid structures have been designed, the trade-off between photoresponsivity and photoresponse speed has not been well balanced. In this work, MoS2 film and In(OH)xSe nanoparticles are combined together to form the hybrid phototransistor. Utilizing both the photoconducting and photogating effects, the photoresponsivity increases about one order of magnitude with a value of 102 A W−1. The ratio of photocurrent and dark current increases to a value of 104. Considering the slow photo recovery speed, a 2 ms gate voltage pulse is applied after turning off the light, which results in a complete recovery of current. The photoconducting effect, photogating effect and gate voltage stimulation simultaneously promote the superior comprehensive photoresponse performances. This method can be further explored and utilized for realizing high performance photodetectors.

Narrow Bandgap Pb–Sn Perovskites/InGaZnO Hybrid Phototransistors for Near‐Infrared Detection

Inorganic–organic hybrid perovskite thin films have attracted significant attention for developing new types of optoelectronic devices due to their superb optoelectronic properties. Herein, a hybrid phototransistor for near‐infrared (NIR) detection is constructed by capping a narrow bandgap Pb–Sn perovskite layer on top of an indium gallium zinc oxide (IGZO) thin‐film transistor (TFT), with a C60 interlayer acting as the electron transporting layer. The Pb–Sn perovskite layer is precisely spin patterned onto the IGZO TFTs' channel region via a hydrophobic perfluoro(1‐butenyl vinyl ether) (CYTOP) photolithography process. In this configuration, a high‐detectivity (2.24 × 1010 Jones at 900 nm) perovskite–C60–IGZO hybrid infrared phototransistor is achieved, and the narrow bandgap perovskite–IGZO hybrid phototransistor has a sensitive photoresponse down to 1100 nm.