Self-powered broadband photodetectors exhibit excellent self-powered and wide-band photoresponse from visible to infrared region and attract enormous attention due to their promising applications in imaging, sensing, and optical communication. PbSe colloidal quantum dots (CQDs) and halide perovskites nanocrystals (NCs) are commonly used for photodetectors due to their strong absorption capability, tunable bandgap, and high aspect ratio. However, due to suffering from low charge carrier mobility and high trap density, the performance of individual PbSe CQDs and perovskites-based photodetectors is not satisfactory. Integration of PbSe CQDs with inorganic mixed-halide perovskite nanomaterials can provide an opportunity to overcome these drawbacks. In this work, a hybrid nanocomposite of PbSe CQDs blended with all-inorganic mixed halide perovskite NCs is integrated to fabricate bulk-heterojunction-based high-performance photodetectors. The transportation of photogenerated carriers is enhanced by employing electrons-and holes-extracting layers. As a result, the photoresponsivity of 6.16 A W −1 and a specific detectivity of 5.96 × 10 13 Jones with an ON/OFF current ratio of 10 5 is obtained for bulk-heterojunction photodetector ITO/ZnO/PbSe:CsPbBr 1.5 I 1.5 /P3HT/Au in the self-powered mode. Meanwhile, the device performance of the fabricated photodetector is numerically simulated by using Technology Computer-Aided Design software, and the physical mechanisms for photogenerated carriers' transportation are discussed in detail.

With its properties of bandgap tunability, low cost, and substrate compatibility, colloidal quantum dots (CQDs) are becoming promising materials for optoelectronic applications. Additionally, solution-processed organic, inorganic, and hybrid ligand-exchange technologies have been widely used in PbS CQDs solar cells, and currently the maximum certified power conversion efficiency of 9.9% has been reported by passivation treatment of molecular iodine. Presently, there are still some challenges, and the basic physical mechanism of charge carriers in CQDs-based solar cells is not clear. Electrochemical impedance spectroscopy is a monitoring technology for current by changing the frequency of applied alternating current voltage, and it provides an insight into its electrical properties that cannot be measured by direct current testing facilities. In this work, we used EIS to analyze the recombination resistance, carrier lifetime, capacitance, and conductivity of two typical PbS CQD solar cells Au/PbS-TBAl/ZnO/ITO and Au/PbS-EDT/PbS-TBAl/ZnO/ITO, in this way, to better understand the charge carriers conduction mechanism behind in PbS CQD solar cells, and it provides a guide to design high-performance quantum-dots solar cells.

High performance solution-processed infrared photodiodes ITO/ZnO/PbSxSe1−x/Au, in which ternary PbSxSe1−x colloidal quantum dots acts as the active layer and ZnO interlayer acts as electron-transporting layer, have been demonstrated.

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Currently, colloidal quantum dots (CQDs)-based photodetectors are widely investigated due to their low cost and easy integration with optoelectronic devices. The requirements for a high-performance photodetector are a low dark current and a high photocurrent. Normally, photodetectors with a low dark current also possess a low photocurrent, or photodetectors with reduced dark current possess a reduced photocurrent, resulting in low detectivity. In this paper, a solution to suppress dark current and maintain a high photocurrent, i.e., use of poly­(methyl methacrylate) doped with Au nanoparticles (NPs) (i.e., PMMA:Au) as an interlayer for enhanced-performance tandem photodetectors, is presented. Our experimental data showed that the dark current through the tandem photodetector ITO/PEDOT:PSS/PbS:CsSnBr3/ZnO/PMMA:Au/CuSeN/PbS:CsSnBr3/ZnO/Ag is suppressed significantly; meanwhile, a high photocurrent is maintained after a PMMA:Au interlayer has been inserted between two subdetectors. The inserted PMMA:Au interlayer acts as storage nodes for electrons, reducing the dark current through the device; meanwhile, the photocurrent can be enhanced under illumination. As a result, the specific detectivity of the tandem photodetector with 35 nm PMMA:Au interlayer was enhanced significantly from 5.01 × 1012 to 2.7 × 1015 Jones under 300 μW/cm2 532 nm illumination at a low voltage of −1 V as compared to the device without a PMMA:Au interlayer. Further, the physical mechanism of enhanced performance is discussed in detail.

Organic-inorganic hybrid photodetectors attract more and more interest, since they can combine the advantages of both organic and inorganic materials into one device, and broadband photodetectors are widely used in many scientific and industrial fields. In this work, we demonstrate the enhanced-performance solution-processed broadband photodiodes by epitaxially blending organo-lead halide perovskite (MAPbBr) colloidal quantum dots (CQDs) with ternary PbSSe CQDs as the active layer. As a result, the interfacial features of the hetero-epitaxial nanocomposite MAPbBr:PbSSe enables the design and perception of functionalities that are not available for the single-phase constituents or layered devices. By combining the high electrical transport properties of MAPbBr QDs with the highly radiative efficiency of PbSSe QDs, the photodiodes ITO/ZnO/PbSSe:MAPbBr/Au exhibit a maximum photoresponsivity and specific detectivity of 21.48 A W and 3.59 × 10 Jones, 22.16 A W and 3.70 × 10 Jones at room temperature under 49.8 μW cm 532 nm laser and 62 μW cm 980 nm laser, respectively. This is higher than that of the layered photodiodes ITO/ZnO/PbSSe/MAPbBr/Au, pure perovskite (MAPbBr) (or PbSSe) QD-based photodiodes reported previously, and it is also better than the traditional inorganic semiconductor-based photodetectors. Our experimental results indicate that epitaxially-aligned nanocomposites (MAPbBr:PbSSe) exhibit remarkable optoelectronic properties that are traceable to their atomic-scale crystalline coherence, and one can utilize the excellent photocarrier diffusion from PbSSe into the perovskite to enhance the device performance from the UV-visible to infrared region.

Narrow band-gap colloidal quantum dots (CQDs) are promising materials for flexible electronic, such as infrared light photodetectors and solar cells.

In the past few decades, great attention has been paid to the development of IV–VI semiconductor colloidal quantum dots, such as PbSe, PbS and PbSSe, in infrared (IR) photodetectors due to their high photosensitivity, solution-processing and low cost fabrication. IR photodetectors based on field-effect transistors (FETs) showed high detectivity since the transconductance can magnify the drain–source current under certain applied gate voltages. However, traditional lateral FETs usually suffer from low photosensitivity and slow responsivity, which restricts their widespread commercial applications. In this work, therefore, novel vertical FET (VFET) based photodetectors are presented, in which the active layer is sandwiched between porous source electrode and planar drain electrode, resulting to ultrashort channel length. In this way, enhanced photoresponsivity and specific detectivity of 291 A W−1 and 1.84 × 1014 Jones, respectively, can be obtained at low drain–source voltage (VDS) of −1 V and gate voltage (Vg) of −2 V under 100 μW cm−2 illumination intensity, which was better than that of the traditional lateral FET based photodetectors. Therefore, it is promising to fabricate broadband photodetectors with high performance and good stability by this easy approach.