Colloidal quantum dots (CQDs) are emerging as promising materials for the next generation infrared (IR) photodetectors, due to their easy solution processing, low cost manufacturing, size‐tunable ...optoelectronic properties, and flexibility. Tremendous efforts including material engineering and device structure manipulation have been made to improve the performance of the photodetectors based on CQDs. In recent years, benefiting from the facial integration with materials such as 2D structure, perovskite and silicon, as well as device engineering, the performance of CQD IR photodetectors have been developing rapidly. On the other hand, to prompt the application of CQD IR photodetectors, scalable device structures that are compatible with commercial systems are developed. Herein, recent advances of CQD based IR photodetectors are summarized, especially material integration, device engineering, and scalable device structures.
Colloidal quantum dots (CQDs) are emerging as the most promising materials for fabricating infrared (IR) photodetectors because of their unique optoelectronic properties such as tunable bandgap and solution‐processability. The recent progress of CQD based IR photodetectors in material engineering, device structure engineering, and scalable fabrication field has been summarized, and their challenges have been discussed.
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The energy landscape of reduced-dimensional perovskites (RDPs) can be tailored by adjusting their layer width (n). Recently, two/three-dimensional (2D/3D) heterostructures containing n = 1 and 2 RDPs ...have produced perovskite solar cells (PSCs) with >25% power conversion efficiency (PCE). Unfortunately, this method does not translate to inverted PSCs due to electron blocking at the 2D/3D interface. Here we report a method to increase the layer width of RDPs in 2D/3D heterostructures to address this problem. We discover that bulkier organics form 2D heterostructures more slowly, resulting in wider RDPs; and that small modifications to ligand design induce preferential growth of n ≥ 3 RDPs. Leveraging these insights, we developed efficient inverted PSCs (with a certified quasi-steady-state PCE of 23.91%). Unencapsulated devices operate at room temperature and around 50% relative humidity for over 1,000 h without loss of PCE; and, when subjected to ISOS-L3 accelerated ageing, encapsulated devices retain 92% of initial PCE after 500 h.A scheme to control the confinement within 2D/3D perovskite heterostructures results in stable, efficient inverted perovskite solar cells.
Colloidal quantum dots (CQDs) are fast-improving materials for next-generation solution-processed optoelectronic devices such as solar cells, photocatalysis, light emitting diodes, and ...photodetectors. Nanoscale CQDs exhibit a high surface to volume ratio, and a significant fraction of atoms making up the quantum dots are thus located on the surface. CQD surface states therefore play a critical role in determining these materials' properties, influencing luminescence, defect energy levels, and doping type and density. In the past five years, halide ligands were applied to CQD solar cells, and these not only improved charge carrier mobility, but also reduced defects on the surface. With the inclusion of halide ligands, CQD solar cell certified power conversion efficiencies have increased rapidly from an initial 5% in 2010 to the latest certified values over 10%. In this perspective article, we summarize recent advances in ligand engineering that improve the performance of CQD solar cells, focusing on the use of halide inorganic ligands to improve CQD surface passivation and film conductivity simultaneously.
Colloidal quantum dots (CQDs) are fast-improving materials for next-generation solution-processed optoelectronic devices such as solar cells, photocatalysis, light emitting diodes, and photodetectors.
Silicon is widespread in modern electronics, but its electronic bandgap prevents the detection of infrared radiation at wavelengths above 1,100 nanometers, which limits its applications in multiple ...fields such as night vision, health monitoring and space navigation systems. It is therefore of interest to integrate silicon with infrared-sensitive materials to broaden its detection wavelength. Here we demonstrate a photovoltage triode that can use silicon as the emitter but is also sensitive to infrared spectra owing to the heterointegrated quantum dot light absorber. The photovoltage generated at the quantum dot base region, attracting holes from silicon, leads to high responsivity (exceeding 410 A·W
with V
of -1.5 V), and a widely self-tunable spectral response. Our device has the maximal specific detectivity (4.73 × 10
Jones with V
of -0.4 V) at 1,550 nm among the infrared sensitized silicon detectors, which opens a new path towards infrared and visible imaging in one chip with silicon technology compatibility.
The manipulation of the dimensionality and nanostructures based on the precise control of the crystal growth kinetics boosts the flourishing development of perovskite optoelectronic materials and ...devices. Herein, a low‐dimensional inorganic tin halide perovskite, CsSnBrI2−x(SCN)x, with a mixed 2D and 3D structure is fabricated. A kinetic study indicates that Sn(SCN)2 and phenylethylamine hydroiodate can form a 2D perovskite structure that acts as a template for the growth of the 3D perovskite CsSnBrI2−x(SCN)x. The film shows an out‐of‐plane orientation and a large grain size, giving rise to reduced defect density, superior thermostability, and oxidation resistance. A solar cell based on this low‐dimensional film reaches a power conversion efficiency of 5.01 %, which is the highest value for CsSnBrxI3−x perovskite solar cells. Furthermore, the device shows enhanced stability in ambient air.
A templated growth approach, in which the crystallization of a 3D perovskite is guided by a dynamically dominant 2D structure, was established for the fabrication of a low‐dimensional perovskite thin film with an out‐of‐plane orientation and a large grain size. The template growth is enabled by the reduced crystallization barrier of the 2D PEA2SnI4−xSCNx intermediate.
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Highly efficient PbS colloidal quantum dot (QD) solar cells based on an inverted structure have been missing for a long time. The bottlenecks are the construction of an effective p–n heterojunction ...at the illumination side with smooth band alignment and the absence of serious interface carrier recombination. Here, solution‐processed nickel oxide (NiO) as the p‐type layer and lead sulfide (PbS) QDs with iodide ligand as the n‐type layer are explored to build a p–n heterojunction at the illumination side. The large depletion region in the QD layer at the illumination side leads to high photocurrent. Interface carrier recombination at the interface is effectively prohibited by inserting a layer of slightly doped p‐type QDs with 1,2‐ethanedithiol as ligands, leading to improved voltage of the device. Based on this graded device structure design, the efficiency of inverted structural heterojunction PbS QD solar cells is improved to 9.7%, one time higher than the highest efficiency achieved before.
An inverted structural QD solar cell with a p–n heterojunction located at the illumination side is constructed and exhibits remarkably high photocurrent above 27 mA cm−2. The insertion of an intermediate buffer layer effectively reduces interface recombination, giving rise to improved voltage. The power conversion efficiency is improved to 9.7%, which is doubled for inverted structural heterojunction QD solar cells.
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Large‐bandgap perovskites offer a route to improve the efficiency of energy capture in photovoltaics when employed in the front cell of perovskite–silicon tandems. Implementing perovskites as the ...front cell requires an inverted (p–i–n) architecture; this architecture is particularly effective at harnessing high‐energy photons and is compatible with ionic‐dopant‐free transport layers. Here, a power conversion efficiency of 21.6% is reported, the highest among inverted perovskite solar cells (PSCs). Only by introducing a secondary amine into the perovskite structure to form MA1−xDMAxPbI3 (MA is methylamine and DMA is dimethylamine) are defect density and carrier recombination suppressed to enable record performance. It is also found that the controlled inclusion of DMA increases the hydrophobicity and stability of films in ambient operating conditions: encapsulated devices maintain over 80% of their efficiency following 800 h of operation at the maximum power point, 30 times longer than reported in the best prior inverted PSCs. The unencapsulated devices show record operational stability in ambient air among PSCs.
Secondary amine, dimethylamine is intentionally included in MAPbI3 perovskite to improve the rigidity and steric hindrance for water adsorption, giving rise to reduced defect density and enhanced hydrophobicity. Solar cells based on this perovskite structure demonstrate a record certified power conversion efficiency of 20.8% for NiOx‐based inverted perovskite solar cells and excellent operational stability under continuous light soaking.
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Silicon and PbS colloidal quantum dot heterojunction photodetectors combine the advantages of the Si device and PbS CQDs, presenting a promising strategy for infrared light detecting. However, the ...construction of a high-quality CQDs:Si heterojunction remains a challenge. In this work, we introduce an inverted structure photodetector based on n-type Si and p-type PbS CQDs. Compared with the existing normal structure photodetector with p-type Si and n-type PbS CQDs, it has a lower energy band offset that provides more efficient charge extraction for the device. With the help of Si wafer surface passivation and the Si doping density optimization, the device delivers a high detectivity of 1.47 × 1011 Jones at 1540 nm without working bias, achieving the best performance in Si/PbS photodetectors in this region now. This work provides a new strategy to fabricate low-cost high-performance PbS CQDs photodetectors compatible with silicon arrays.
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