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The realization of a controllable transparent conducting system with selective light transparency is crucial for exploring many of the most intriguing effects in top‐illuminated optoelectronic devices. However, the performance is limited by insufficient electrical conductivity, low work function, and vulnerable interface of traditional transparent conducting materials, such as tin‐doped indium oxide. Here, it is reported that two‐dimensional (2D) titanium carbide (Ti3C2Tx) MXene film acts as an efficient transparent conducting electrode for the lead sulfide (PbS) colloidal quantum dots (CQDs) photodiode with controllable near infrared transmittance. The solution‐processed interface engineering of MXene and PbS layers remarkably reduces the interface defects of MXene/PbS CQDs and the carrier concentration in the PbS layer. The stable Ti3C2Tx/PbS CQDs photodiodes give rise to a high specific detectivity of 5.51 × 1012 cm W−1 Hz1/2, a large dynamic response range of 140 dB, and a large bandwidth of 0.76 MHz at 940 nm in the self‐powered state, ranking among the most exceptional in terms of comprehensive performance among reported PbS CQDs photodiodes. In contrast with the traditional photodiode technologies, this efficient and stable approach opens a new horizon to construct widely used infrared photodiodes with CQDs and MXenes. [ABSTRACT FROM AUTHOR]

We report on a novel optical fire detector based on a PbS colloidal quantum dot photodetector. The sensor is realized with a simple, cost effective, drop casting technique. The photodetector is characterized in terms of its electrical characteristics, responsivity, and specific detectivity to monochromatic light. We demonstrate effective indoor fire detection at a distance exceeding 20 m with a 120° field of view. We also show a twofold improvement of the detector signal to noise ratio exploiting a short focal lens. [ABSTRACT FROM PUBLISHER]

Lead sulfide (PbS) colloidal quantum dots (CQDs) solar cells possess the advantages of absorption into the infrared, solution processing, and multiple exciton generation, making them very competitive as a low-cost photovoltaic alternative. Employing an n-i-p ZnO/tetrabutylammonium (TBAI)-PbS/ethanedithiol (EDT)-PbS device configuration, the present study reports a 9.0% photovoltaic device through ZnMgO electrode engineering and graphene doping. Sol-gel-derived Zn0.9Mg0.1O buffer layer shows better transparency and higher conduction band maximum than ZnO, and incorporation of graphene and chlorinated graphene oxide into the TBAI-PbS and EDT-PbS layer respectively boosts carrier collection, leading to device with significantly enhanced open circuit voltage and short-circuit current density. It is believed that incorporation of graphene into PbS CQD film as proposed here, and more generally nanosheets of other materials, would potentially open a simple and powerful avenue to overcome the carrier transport bottleneck of CQD optoelectronic device, thus pushing device performance to a new level. [ABSTRACT FROM AUTHOR]

PbS colloidal quantum dot (CQD) infrared photodiodes have attracted wide attention due to the prospect of developing cost-effective infrared imaging technology. Presently, ZnO films are widely used as the electron transport layer (ETL) of PbS CQDs infrared photodiodes. However, ZnO-based devices still suffer from the problems of large dark current and low repeatability, which are caused by the low crystallinity and sensitive surface of ZnO films. Here, we effectively optimized the device performance of PbS CQDs infrared photodiode via diminishing the influence of adsorbed H 2 O at the ZnO/PbS CQDs interface. The polar (002) ZnO crystal plane showed much higher adsorption energy of H 2 O molecules compared with other nonpolar planes, which could reduce the interface defects induced by detrimentally adsorbed H 2 O. Based on the sputtering method, we obtained the [002]-oriented and high-crystallinity ZnO ETL and effectively suppressed the adsorption of detrimental H 2 O molecules. The prepared PbS CQDs infrared photodiode with the sputtered ZnO ETL demonstrated lower dark current density, higher external quantum efficiency, and faster photoresponse compared with the sol-gel ZnO device. Simulation results further unveiled the relationship between interface defects and device dark current. Finally, a high-performance sputtered ZnO/PbS CQDs device was obtained with a specific detectivity of 2.15 × 10 12 Jones at -3 dB bandwidth (94.6 kHz).

PbS colloidal quantum dots passivated by the thiocyanate anion (SCN - ) are developed to combine with perovskite (CH 3 NH 3 PbI 3 ) as building blocks for UV-vis-NIR broadband photodetectors. Both high electrical conductivity and appropriate energy-level alignment are obtained by the in situ ligand exchange with SCN - . The PbS-SCN/CH 3 NH 3 PbI 3 composite photodetectors are sensitive to a broad wavelength range covering the UV-vis-NIR region (365-1550 nm), possessing an excellent responsivity of 255 A W -1 at 365 nm and 1.58 A W -1 at 940 nm, remarkably high detectivity of 4.9 × 10 13 Jones at 365 nm and 3.0 × 10 11 Jones at 940 nm, and fast response time of ≤42 ms. Furthermore, a 10 × 10 photodetector array is fabricated and integrated, which constitutes a high-performance broadband image sensor. Our approach paves a way for the development of highly sensitive broadband photodetectors/imagers that can be easily integrated.

Photodetectors convert photons into current or voltage outputs and are thus widely used for spectroscopy, imaging and sensing. Traditional photodetectors generally show a consistent-polarity response to incident photons within their broadband responsive spectrum. Here we introduced a new type of photodetector employing SnS 2 nanosheets sensitized with PbS colloidal quantum dots (CQDs) that are not only sensitive (~10 5  A W -1 ) and broadband (300-1000 nm) but also spectrally distinctive, that is, show distinctive (positive or negative) photoresponse toward incident photons of different wavelengths. A careful mechanism study revealed illumination-modulated Schottky contacts between SnS 2 nanosheets and Au electrodes, altering the photoresponse polarity toward incident photons of different wavelengths. Finally, we applied our SnS 2 nanosheet/PbS CQDs hybrid photodetector to differentiate the color temperature of emission from a series of white light-emitting diodes (LEDs), showcasing the unique application of our novel photodetectors., Competing Interests: The authors declare no conflict of interest.