Ag nanoparticles at p-Si/ MAPbI3 perovskite interface: improved photo responsivity and response speed in photodetection.

Although enhanced performances of photovoltaic devices by embedding metal nanoparticals in charge transport layer, doping into active layer bulk, decorating the active layer surface, and inserting at the interface between semiconductor and the electrode were reported, the effect of incorporating metal NPs at the interface of single crystal semiconductor and perovskite is rarely tackled. Herein the effects of incorporating Ag nanoparticals (AgNPs) at p-Si/MAPbI3 perovskite interface on the photodiode performances were investigated. The results showed that compared with reference device (without AgNPs) the photoresponsivity of the device incorporating AgNPs is greatly improved with the exception for light with wavelengths fall in the spectral range where AgNPs have strong optical absorption. This effect is extremely significant for relatively shorter wavelengths in visible region, and a maximal improvement of around 10.6 times in photoresponsivity was achieved. The physical origin of the exception for spectral range that AgNPs have strong optical absorption is the cancelation of scatter resulted enhancement through AgNPs by band-to-band absorption resulted reduction of photocurrent, in which the generated electron has energy near the fermi level and the hole has large effective mass, which relax by nonradiative recombination, thus making not contribution to the photocurrent. More importantly, the AgNP decorated device showed much faster photo response speed than reference device, and a maximal improvement of around 7.9 times in rise and fall time was achieved. These findings provide a novel approach for high responsive and high speed detection for weak light.

Facile Vertical Structure Broadband Photodetectors Enabled by Polyvinylpyrrolidone-Regulated Perovskite and Near-Infrared-Sensitive Lead Phthalocyanine.

Broadband photodetectors have drawn tremendous attention in many application areas such as imaging, optical communication, and biochemical sensing. Perovskite is a star material with broad spectral absorption, but it is challenging to develop ultraviolet-visible-near-infrared (UV-Vis-NIR) ultra-broadband photodetectors due to the insufficient absorption in the near-infrared region. Moreover, it is difficult to construct a diode-type photodetector with a simple vertical structure based only on perovskite materials. Here, facile vertical structure broadband photodetectors were fabricated based on heterojunctions that were composed of perovskite MAPbI3 films with UV-Vis absorption spectrum and small organic molecule lead phthalocyanine (PbPc) with strong NIR optical absorption, resulting in UV-Vis-NIR ultra-broadband photodetection. The quality of MAPbI3 films was improved by introducing polyvinylpyrrolidone (PVP) modification, and subsequently, the corresponding MAPbI3/PbPc heterojunction-based photodetectors exhibited rectification characteristics and reduced reverse dark currents. When the PVP mass ratio is 1 wt%, the photodetector achieved the best performance that the spectral response uniformity factor was as high as 0.77, the photoresponsivity exceeded 10 A/W, and the photoresponse time was less than 0.5 ms under a light intensity of 0.013 mW/cm2 in the UV-Vis to NIR spectral range. These results are comparable or superior to those of some inorganic, organic, and perovskite photodetectors reported previously. This study would provide an effective strategy to construct high-performance perovskite photodetectors based on a simple vertical structure, paving the way to the realization of UV-Vis-NIR broadband photodetection.

Towards high photoresponse of perovskite nanowire/copper phthalocyanine heterostructured photodetector.

One-dimensional nanowire structures composed of perovskite are widely recognized for their exceptional optoelectronic performance and mechanical properties, making them a popular area of investigation in photodetection research. In this work, a perovskite nanowire/copper phthalocyanine heterojunction-based photodetector was fabricated, which exhibits high photoresponse in the visible-near-infrared region. The incorporation of a heterojunction significantly enhanced the photoelectric performance. Specifically, the photoresponsivity and external quantum efficiency of the nanowire-based device were elevated from 58.5 A W-1and 1.35 × 104% to 84.5 A W-1and 1.97 × 104% at 532 nm, respectively. The enhanced photoresponse of the heterojunction device can be attributed to the unique microstructure of nanowire arrays. The wrapping of the nanowires by copper phthalocyanine forms heterojunctions with a larger dissociation area, which facilitated exciton dissociation and enhanced device performance. This work provides a promising example for optimizing the performance of nanowire devices.

Thickness-ratio-dependent performances of broadband organic photodiodes based on a tin phthalocyanine/PTCDA heterojunction.

Employing a photosensitive donor/acceptor planar heterojunction (DA-PHJ) with complementary optical absorption as the active layer is one of the key strategies for realizing broad spectral organic photodiodes (BS-OPDs). To achieve superior optoelectronic performance, it is vital to optimize the thickness ratio of the donor layer to acceptor layer (the DA thickness ratio) in addition to the optoelectronic properties of the DA-PHJ materials. In this study, we realized a BS-OPD exploiting tin(II) phthalocyanine (SnPc)/3,4,9,10-perylenete-acarboxylic dianhydride (PTCDA) as the active layer and investigated the effect of the DA thickness ratio on the device performance. The results showed that the DA thickness ratio has a significant impact on the device performance, and an optimized DA thickness ratio of 30:20 was found. Upon the optimization of the DA thickness ratio, improvements of 187% in photoresponsivity and 144% in specific detectivity were achieved on average. Trap-free space-charge-limited photocarrier transport and balanced optical absorption over the wavelength range can be ascribed to the improved performance at the optimized DA thickness ratio. These results establish a solid photophysical foundation for improving the performance of BS-OPDs via thickness ratio optimization.

Ultranarrow-band filterless photodetectors based on CH3NH3PbClxBr3-xmixed-halide perovskite single crystals.

Narrow-band photodetectors based on halide perovskite have recently attracted significant attention due to their exceptional narrow-band detection performance and tunable absorption peaks covering a wide optical range. In this work, we report mixed-halide CH3NH3PbClxBr3-xsingle crystal-based photodetectors have been fabricated, where the Cl/Br ratios were varied (3:0, 10:1, 5:1, 1:1, 1:7, 1:14 and 0:3). Vertical and parallel structures devices were fabricated which exhibited ultranarrow spectral responses under bottom illumination, with a full-width at half-maximum less than 16 nm. The observed performance can be ascribed to the unique carrier generation and extraction mechanisms within the single crystal under short and long wavelength of illumination. These findings offer valuable insights into the development of narrow-band photodetectors that do not necessitate the use of filters and hold tremendous potential for a diverse array of applications.

Significant Detectivity Enhancement of Broad Spectral Organic-Inorganic Hybrid Photodiodes by C60 Film as Hole-Blocking Layer.

As an important classification of photodetectors, broad spectral photodiodes are ubiquitous in the fields of industry and scientific research. Here, we reported a type of broad spectral organic-inorganic hybrid photodiodes (OIHPDs) based on planar-bulk heterojunction, which composed of 3,4,9,10-perylenetertracarboxylic dianhydride (PTCDA), copper phthalocyanine (CuPc) and fullerene (C60). In our research, the dark current of the OIHPD with 10 nm C60 film (10 nm-C60 OIHPD) was as low as 25.6 µA, which is about 63 times smaller than the dark current of the OIHPD without C60 film (C60-free OIHPD). It is considered that the significantly enhanced performance of 10 nm-C60 OIHPD is attributed to the introduction of the C60 film, which act as hole-blocking layer to reduce the dark current. And through the schematic energy level model combined with experimental measurements, the reason for the dark current change was well explained. Furthermore, the specific detectivity of 10 nm-C60 OIHPD was almost one order of magnitude larger than it of C60-free OIHPD, and a notable enhancement of over 1011 cm Hz1/2/W was obtained due to the fiercely reduced dark current. These results provide insights on how to improve the performance of organic photodiodes.

Channel-length-dependent performance of photosensitive organic field-effect transistors.

Pentacene is a small molecule organic semiconductor and has high absorption in the UV and visible region. In this work, we report the channel-length-dependent performance of bottom-gate top-contact photosensitive organic field-effect transistors based on pentacene with different channel lengths ranging from 25 to 150 µm. The results show that, for a given drain voltage, the photoresponsivity, external quantum efficiency, and specific detectivity decrease with increasing channel length. For a given channel length and gate voltage, the photoresponsivity, external quantum efficiency, and specific detectivity increase with drain voltages, and then tend to saturate at high drain voltages.

Achieving Weak Light Response with Plasmonic Nanogold-Decorated Organic Phototransistors.

Weak light response of organic photodetectors has fascinating potentials in fields of modern science and technology. However, their photoresponsivity is hindered by poor photocarrier excitation and transport. Decorating active-layer surface with plasmonic nanometals is considered a viable strategy to address this issue. Here, we demonstrate a plasmonic nanogold decorated organic phototransistor achieving remarkable enhancement of photoresponsivity. Meanwhile, the photoresponsive range is broadened by 4 orders of magnitude. The proposed design is substantiated by a schematic energy level model combined with theoretical simulation analysis, enabling the development of the advanced optoelectronics.

Notably Improved Red Photoresponse of Organic Diode Employing Gold Nanoparticles Plasmonic Absorption.

The wide variation of optical absorptions of AuNPs provides a strategy to fabricate simple photosensitive sensors. We demonstrate a notably improved red photoresponse of organic diode by incorporation of 3-nm gold nanoparticles (AuNPs) into NPB/C60 heterojunction interface. Near-field enhancement around AuNPs gives rise to the significant improvement of exciton generation and dissociation in the interface of organic photodiode (OPD), thereby obtaining a sharply increasing photocurrent. A detailed energy level diagram is proposed to interpret the improvement of photocurrent. Significantly, the OPD exhibits excellent diode characteristics in the dark. On the other hand, the device shows a large red photoresponse with responsivity greater than 200 mA/W. The calculated maximum D* and EQE are 1.52 x 10(11) jones and 39.21% at a very low voltage of -0.5 V, respectively. Note that the NPB and C60 almost have no absorption at 650 nm; the red photoresponse performance above is one of the highest values reported thus far for the single AuNPs layer dominant OPDs. It is expected that such a red-light detector will have potential application in future optoelectronic devices.

High Performance Photodiode Based on p-Si/Copper Phthalocyanine Heterojunction.

Hybrid organic-inorganic (HOI) photodiodes have both advantages of organic and inorganic materials, including compatibility of traditional Si-based semiconductor technology, low cost, high photosensitivity and high reliability, showing tremendous value in application. Red light sensitive HOI photodiodes based on the p-Si/copper phthalocyanine (CuPc) hetrojunction were fabricated and characterized. The effects of CuPc layer thickness on the performance were investigated, and an optimal layer thickness of around 30 nm was determined. An analytical expression is derived to describe the measured thickness dependence of the saturation photocurrent. For the device with optimal CuPc layer thickness, a photoresponsivity of 0.35 A/W and external quantum efficiency of 70% were obtained at 9 V reverse voltage bias and 655 nm light illumination of 0.451 mW. Furthermore, optical power dependent performances were investigated.

High-performance organic broadband photomemory transistors exhibiting remarkable UV-NIR response.

The electrical and optical properties of organic semiconductors have improved rapidly in recent years, rendering them highly promising for various optoelectronic applications owing to low-cost and lightweight potential in combination with spectral tunability and long photocarrier lifetimes. Organic photomemory has emerged as an innovative application to achieve optical data storage. However, practical operation requires universal device design with broader spectral response in terms of related materials, interfaces and architecture, a task that remains a significant challenge. Herein, we present a universal strategy to fabricate organic broadband photomemories featuring remarkable UV-NIR response, thereby providing optical switching ability with a controllable memory window. To the best of our knowledge, this study demonstrates an excellent performance with the broadest response spectra and the highest photomemory efficiency of up to 593%. We systematically study the charge trapping mechanism and photoinduced injection enhancement by combining an energy level model with theoretical calculations, characterizing conceivable photogenerated minority carrier trapping and accumulation kinetics. Thus, it is anticipated that the proposed approach will be a starting point for further research, resulting in high-performance organic photomemory ideal for digital commutation between optical and electric signals.

Remarkably enhanced red-NIR broad spectral absorption via gold nanoparticles: applications for organic photosensitive diodes.

For organic films, remarkably enhanced red-NIR broad spectral absorption was achieved via the incorporation of gold nanoparticles (AuNPs) using a simple and facile preparation. The relevant thermal evaporation method has produced size-controllable AuNPs in the range of 0-20 nm diameter. The potential use of localized surface plasmon resonance (LSPR) enhanced organic photosensitive diodes (OPDs) as sensitive broadband sensors was discussed in this context. Here we showed that, by combining organic heterojunctions with size-controllable plasmonic AuNPs, the efficiency of organic photodetectors could be increased by up to one order of magnitude, because of LSPR and scattering effects of the AuNPs. Fabricated OPD devices showed a large photoresponse under radiation from wavelengths between 650 and 830 nm, accompanied by a low power consumption profile. A schematic energy level model combined with theoretical simulation analysis was proposed to explain the experimental data. More importantly, to the best of our knowledge, this work demonstrated the broadest photosensitivity with high responsivity from AuNP-based photodetectors, proving the potential of AuNPs as a promising material for efficient optoelectronic devices.

Ultrahigh near infrared photoresponsive organic field-effect transistors with lead phthalocyanine/C60 heterojunction on poly(vinyl alcohol) gate dielectric.

Performances of photoresponsive organic field-effect transistors (photOFETs) operating in the near infrared (NIR) region utilizing SiO2 as the gate dielectric is generally low due to low carrier mobility of the channel. We report on NIR photOFETs based on lead phthalocyanine (PbPc)/C60 heterojunction with ultrahigh photoresponsivity by utilizing poly(vinyl alcohol) (PVA) as the gate dielectric. For 808 nm NIR illumination of 1.69 mW cm(-2), an ultrahigh photoresponsivity of 21 A W(-1), and an external quantum efficiency of 3230% were obtained at a gate voltage of 30 V and a drain voltage of 80 V, which are 124 times and 126 times as large as the reference device with SiO2 as the gate dielectric, respectively. The ultrahigh enhancement of photoresponsivity is resulted from the huge increase of electron mobility of C60 film grown on PVA dielectric. AFM investigations revealed that the C60 film grown on PVA is much smooth and uniform and the grain size is much larger than that grown on SiO2 dielectric, which together results in four orders of magnitude increase of the field-effect electron mobility of C60 film.

Position-dependent performance of copper phthalocyanine based field-effect transistors by gold nanoparticles modification.

A facile fabrication and characteristics of copper phthalocyanine (CuPc)-based organic field-effect transistor (OFET) using the gold nanoparticles (Au NPs) modification is reported, thereby achieving highly improved performance. The effect of Au NPs located at three different positions, that is, at the SiO2/CuPc interface (device B), embedding in the middle of CuPc layer (device C), and on the top of CuPc layer (device D), is investigated, and the results show that device D has the best performance. Compared with the device without Au NPs (reference device A), device D displays an improvement of field-effect mobility (µ(sat)) from 1.65 × 10(-3) to 5.51 × 10(-3) cm(2) V(-1) s(-1), and threshold voltage decreases from -23.24 to -16.12 V. Therefore, a strategy for the performance improvement of the CuPc-based OFET with large field-effect mobility and saturation drain current is developed, on the basis of the concept of nanoscale Au modification. The model of an additional electron transport channel formation by FET operation at the Au NPs/CuPc interface is therefore proposed to explain the observed performance improvement. Optimum CuPc thickness is confirmed to be about 50 nm in the present study. The device-to-device uniformity and time stability are discussed for future application.