Perovskite Quantum Dots Films Research Articles

High-efficiency red perovskite quantum dot light-emitting diodes via an effective cation exchange method for tunable emission wavelength

The utilization of perovskite quantum dots (PQDs) in photoelectric devices is indeed an area of intense research due to their advantageous properties such as tunability of visible light and efficient light emission. In this study, mixed CsPbI3 and FAPbI3 PQD dispersions were successfully employed for cation exchange to prepare red-color Cs1−xFAxPbI3 PQD with the photoluminescence (PL) wavelength from 689 nm (x = 0) to 778 nm (x = 1). It is also found that the aggregation of Cs1−xFAxPbI3 PQD films were strongly dependent on x. When x from 0 to 0.6, the holes in PQD thin films were gradually improved. On the opposite, when x > 0.6, the PQDs thin films returned more and more holes due to an excess of FA + cations. The resulting Cs1-xFAxPbI3 PQD based light-emitting diodes (LEDs) also demonstrated tunable emission wavelengths, and it is worth mentioning that the maximum external quantum efficiency (EQE) of 11.22 % was achieved with an emission wavelength of 758 nm when x = 0.6.

Long-range order enabled stability in quantum dot light-emitting diodes.

Light-emitting diodes (LEDs) based on perovskite quantum dots (QDs) have produced external quantum efficiencies (EQEs) of more than 25% with narrowband emission1,2, but these LEDs have limited operating lifetimes. We posit that poor long-range ordering in perovskite QD films-variations in dot size, surface ligand density and dot-to-dot stacking-inhibits carrier injection, resulting in inferior operating stability because of the large bias required to produce emission in these LEDs. Here we report a chemical treatment to improve the long-range order of perovskite QD films: the diffraction intensity from the repeating QD units increases three-fold compared with that of controls. We achieve this using a synergistic dual-ligand approach: an iodide-rich agent (aniline hydroiodide) for anion exchange and a chemically reactive agent (bromotrimethylsilane) that produces a strong acid that in situ dissolves smaller QDs to regulate size and more effectively removes less conductive ligands to enable compact, uniform and defect-free films. These films exhibit high conductivity (4 × 10-4 S m-1), which is 2.5-fold higher than that of the control, and represents the highest conductivity recorded so far among perovskite QDs. The high conductivity ensures efficient charge transportation, enabling red perovskite QD-LEDs that generate a luminance of 1,000 cd m-2 at a record-low voltage of 2.8 V. The EQE at this luminance is more than 20%. Furthermore, the stability of the operating device is 100 times better than previous red perovskite LEDs at EQEs of more than 20%.

Passivation of 2D Cs2PbI2Cl2 Nanosheets for Efficient and Stable CsPbI3 Quantum Dot Solar Cells.

Inorganic CsPbI3 perovskite quantum dots (PQDs) possess remarkable optical properties, making them highly promising for photovoltaic applications. However, the inadequate stability resulting from internal structural instability and the complex external surface chemical environment of CsPbI3 PQDs has hindered the development of CsPbI3 PQD solar cells (PQDSCs). In this work, the capping layer composed of inorganic two-dimensional (2D) Ruddlesden-Popper (RP) phase Cs2PbI2Cl2 nanosheets (NSs) is introduced, which may be effectively treated to improve the surface properties of the CsPbI3 PQD film. This modification serves to passivate defects by filling cesium and iodine vacancies while optimizing the energy band arrangement and preventing humidity intrusion, leading to the meliorative stability and photovoltaic performance. The optimized CsPbI3 PQDSCs achieve an enhanced power conversion efficiency (PCE) of 14.73%, with the superb stability of only a 16% efficiency loss after being exposed to ambient conditions (30 ± 5% RH) for 432 h.

Ultrahigh-performance indoor perovskite quantum dot photovoltaics via ligand-passivation engineering

The advancement of perovskite photovoltaic (PePV) systems for harnessing indoor light energy has been accelerated by the advent of the Internet of Things (IoT). However, the commercialization of these systems is impeded by moisture instability and restricted carrier lifetimes. Perovskite quantum dots (PQDs) offer viable solutions for increasing stability despite the potential effects of their organic ligands on efficiency. In this study, a ligand passivation strategy was employed in PQD photovoltaics (PQDPVs) to enhance the carrier lifetime. The inclusion of 2-phenyl-4-(1,2,2-triphenylvinyl) quinazoline (2PACz) in the PQD film effectively reduced surface defects and suppressed trap-assisted charge recombination, resulting in a prolonged carrier lifetime. The charge carrier lifetimes in passivated PQDPVs increased by 35 %. Additionally, the matching of the energy level of the PQD changed after 2PACz passivation engineering with that of the 2PACz showed an advantage for hole transport. PQDPVs fabricated using 2PACz-passivated PQDs showed an impressive output power density (Pout) of 123.3 µW/cm2 (power conversion efficiency of 41.1 %) under a fluorescent lamp (0.30 mW/cm2; 1000 lx) owing to improved open-circuit voltage and fill factor. Moreover, the device maintained more than 80 % of its initial efficiency for 500 h in an ambient atmosphere. These findings highlight the potential of PQDPVs to compete with conventional PePVs for application in self-powered optoelectronic devices under dim illumination.

Modified surface ligand management of CsPbI3 perovskite quantum dots enables efficient and stable electroluminescent solar cells

Solution-processed CsPbI3 perovskite quantum dots (PQDs) have attracted enormous attention in both photovoltaic and electroluminescent applications in recent years. However, the surface defects of CsPbI3 PQDs in the ligand exchange procedure still suffer the challenge of imperfect passivation, leading to poor device performance and ambient stability. In this work, we propose a modified surface ligand management to deposit CsPbI3 PQD films using a layer-by-layer (LBL) solid-state exchange strategy, and its applications in photovoltaic and electroluminescent devices are studied. The conjugated phenethylammonium iodide (PEAI) ligand, acting as a short-chain ligand with a phenyl group (PEA+ ion) for encapsulating the CsPbI3 PQDs during the LBL procedure, which can both realize enhanced inter-dot coupling and defects passivation compared with conventional post-treatments. We further demonstrate the balanced transport and injection of electrons and holes within the PEAI-LBL based CsPbI3 PQD films. With this approach, the CsPbI3 PQD solar cells based on PEAI-LBL yielded a champion power conversion efficiency (PCE) of up to 14.18% with a high open voltage of 1.23 V, along with obviously electroluminescent red emission properties in one device. Meanwhile, the unencapsulated devices exhibited excellent stability under a high-humidity environment. This strategy should accelerate advancement in utilizing PQDs for bifunctional optoelectronic applications.

Highly Luminescent and Stable Perovskite Quantum Dots Films for Light‐Emitting Devices and Information Encryption

AbstractThe inherent flexibility and excellent mechanical strength of lead halide perovskite quantum dots (LHP‐QDs) films have attracted much attention in the fields of flexible lighting, displays, non‐planar x‐ray imaging, and wearable optoelectronics. Unfortunately, the complicated synthesis process and poor stability limit its practical applications, hence there is an urgent need to develop a feasible fabrication process for films to attain high device performance. Herein, a molecular level hybridization of bridged polysilsesquioxane (BPSQ) is designed as matrix to harvest both flexibility of organics and stability of inorganics, resulting in improved interfacial compatibility between the CsPbBr3 QDs and the matrix through chemical bond anchoring. The CsPbBr3@3‐aminopropyl‐triethoxysilane (APTES)@BPSQ films showcase bright narrow‐band photoluminescence, with a photoluminescence quantum yield of 61% and a half‐peak full width at half maximum of <17 nm. Notably, these films demonstrate excellent environmental stability, UV resistance, water stability (experiencing only an 18% decrease in luminescence intensity after 168 h of water immersion), and high‐temperature stability (withstanding temperatures up to 500 K). Furthermore, white light‐emitting diodes (WLEDs) and anti‐counterfeiting patterns have been fabricated using CsPbBr3@APTES@BPSQ, highlighting their wide application potential in flexible light‐emitting devices and information encryption.

Large-scale preparation of CsPbBr3 perovskite quantum dot/EVA composite adhesive film by melting for crystal silicon solar cell

Silicon solar cell is the most mature photovoltaic conversion device, and in order to further improve the performance of the device, application of downshifting films has become a research hotspot. In this paper, CsPbBr3 perovskite quantum dot/EVA composite adhesive film was prepared by melting method with CsPbBr3 perovskite quantum dot film under solution processing as masterbatch and EVA particles as excipient. The effect of synthesis conditions on the luminescence properties of the composite films were thoroughly studied. The optimized CsPbBr3 perovskite quantum dot/EVA composite adhesive film has excellent performance, and its light transmission reaches 85%. The CsPbBr3 perovskite quantum dot/EVA composite adhesive film absolutely improves the efficiency of silicon solar cells by 1.08%, which is much higher than that of pure EVA adhesive film (0.63%). In addition, the device efficiencies have almost no change after 30 d in the air, maintaining the working stability of the device and contributing to industrial applications. This study provides a novel, industrial and low-cost synthesis route for the synthesis of CsPbBr3 perovskite quantum dot/EVA composite adhesive film, which is expected to have broad application.

Multi-color transparent display based on perovskite quantum dots fabricated by laser-induced plasma etching.

Display technology is being revolutionized by cutting-edge transparent displays that can provide visual information on the screen while allowing the surrounding environment to be visible. In this report, a new method is proposed for patterning displays based on perovskite quantum dots (PQDs) on glass surfaces. A glass substrate with a polyvinylidene fluoride (PVDF) constraint layer is patterned using laser-induced plasma etching, and then a PQDs film is spin-coated on the etched sample. The PQDs pattern on the glass substrate is obtained after peeling off the PVDF constraint layer. The thickness of the film is obtained by carrying out simulations. The plasma output from different metal targets is recorded and analyzed to select the most suitable parameters and materials for improvement of the patterning accuracy. The transparent pattern display of PQDs is realized with an accuracy of 10-20 µm and a burial depth of about 1 µm. This method allows PQDs to be encapsulated under the substrate surface, which decreases the susceptibility of environmental impact. Additionally, encapsulation prevents the quantum dots from leaking out and causing environmental pollution. The proposed method has potential in the design of transparent displays and anti-counterfeiting applications.

Fostering the Dense Packing of Halide Perovskite Quantum Dots through Binary-Disperse Mixing.

Due to their versatile applications, perovskite quantum dot (PQD)-based optoelectrical devices have garnered significant research attention. However, the fundamental packing behavior of PQDs in thin films and its impact on the device performance remain relatively unexplored. Drawing inspiration from theoretical models concerning packing density with size mixtures, this study presents an effective strategy, namely, binary-disperse mixing, aimed at enhancing the packing density of PQD films. Comprehensive grazing-incidence small-angle X-ray characterization suggested that the PQD film consists of three phases: two monosize phases and one binary mixing phase. The volume fraction and population of the binary-size phase can be tuned by mixing an appropriate amount of large and small PQDs. Furthermore, we performed multi-length-scale all-atom and coarse-grained molecular dynamics simulations to elucidate the distribution and conformation of organic surface ligands, highlighting their influence on PQD packing. Notably, the mixing of two PQDs of different sizes promotes closer face-to-face contact. The densely packed binary-disperse film exhibited largely suppressed trap-assisted recombination, much longer carrier lifetime, and thereby improved power conversion efficiency. Hence, this study provides fundamental understanding of the packing mechanism of perovskite quantum dots and highlights the significance of packing density for PQD-based solar cells.

Interface-Induced Crystallinity Enhancement of Perovskite Quantum Dots for Highly Efficient Light-Emitting Diodes.

Perovskite quantum dot light-emitting diodes (QLEDs) with high color purity and wide color gamut have good application prospects in the next generation of display technology. However, colloidal perovskite quantum dots (PQDs) may introduce a large number of defects during the film-forming process, which is not conducive to the luminous efficiency of the device. Meanwhile, the disordered film formation of PQDs will form interfacial defects and reduce the device performance. Here, we report an interface-induced crystallinity enhancement (IICE) strategy to increase the crystallinity of PQDs at the hole transport layer (HTL)/PQD interface. As a result, both the Br- vacancies in the PQD film and the interfacial defects were well passivated and the leakage current was also suppressed. We achieved QLEDs with a maximum external quantum efficiency (EQE) of 16.45% and current efficiency (CE) of 61.77 cd/A, showing improved performance to more than twice that of the control devices. The IICE strategy paves a new way to enhance the crystallinity of PQD films, so as to improve the performance of QLEDs for application in the future display field.

Simple approach for electronic structure calculations on self-organized perovskite quantum dot films

Simple approach for electronic structure calculations on self-organized perovskite quantum dot films

Perovskite Quantum Dot Light-Emitting Memcapacitor

Perovskite quantum dots (PQDs) are promising in the field of light-emitting diodes (LEDs) due to their adjustable band gap, high photoluminescence quantum yield, and high color purity. However, ion migration is prone to occur in the device due to the structural instability of PQDs, resulting in the degradation of external quantum efficiency. In this work, we proposed a strategy to realize a perovskite quantum dot light-emitting memcapacitor (PQLEM) so as to enhance the electroluminescent performance of PQDs. By varying the pre-bias voltage and time, the ion distribution and trap density in the PQD film could be modified, thereby affecting the capacitance value and luminous efficiency of the device. Under the memcapacitive effect, the external quantum efficiency (EQE) of the device increases from an initial 2.81 to 7.95%. This work provides a route for achieving perovskite quantum dot light-emitting devices with high luminous efficiency.

Latest Advances in Narrow‐Band Phosphors and Their Role in Color Management

Latest Advances in Narrow‐Band Phosphors and Their Role in Color Management

Hybrid Ligand Polymerization for Weakly Confined Lead Halide Perovskite Quantum Dots

Rational ligand passivation is essential to achieve a higher performance of weakly confined lead halide perovskite quantum dots (PQDs) via a mechanism of surface chemistry and/or microstrain. In situ passivation with 3-mercaptopropyltrimethoxysilane (MPTMS) produces CsPbBr3 PQDs with an enhanced photoluminescence quantum yield (PLQY, ΦPL) of up to 99%; meanwhile, charge transport of the PQD film can be enhanced by one order of magnitude. Herein, we examine the effect of the molecular structure of MPTMS as the ligand exchange agent in comparison to octanethiol. Both thiol ligands promote crystal growth of PQDs, inhibit nonradiative recombination, and cause blue-shifted PL, while the silane moiety of MPTMS manipulates surface chemistry and outperforms owing to its unique cross-linking chemistry characterized by FTIR vibrations at 908 and 1641 cm-1. Emergence of the diagnostic vibrations is ascribed to hybrid ligand polymerization arising from the silyl tail group that confers the advantages of narrower size dispersion, lower shell thickness, more static surface binding, and higher moisture resistance. In contrast, the superior electrical property of the thiol-passivated PQDs is mostly determined by the covalent S-Pb bonding on the interface.

15.1: Invited Paper: Novel method for preparing blue perovskite light emitting pixel diodes

Traditional inkjet printing color quantum dot technology is to print red, green and blue quantum dot inks respectively, while perovskite material is ionic compound, and changing the halogen component can change the light color, which provides a new method for inkjet printing to realize color display. Here, we report a method for implementing blue devices by ion exchange between halogen‐containing inks and underlying perovskite quantum dot films by inkjet‐printing. This method can also be used for full‐color devices.

Dual Ions Passivating FAPbBr3 Perovskite Quantum Dot Films via a Vacuum Drying Method for Stable and Efficient Solar Cells with an Ultrahigh Open-Circuit Voltage of over 1.67 V

Dual Ions Passivating FAPbBr₃ Perovskite Quantum Dot Films via a Vacuum Drying Method for Stable and Efficient Solar Cells with an Ultrahigh Open-Circuit Voltage of over 1.67 V

Manipulation of the photoluminescence of lead halide perovskite quantum dots with mechanically reconfigurable 3D photonic crystals.

Reconfigurable 3D photonic crystals (3DPCs) are promising for dynamic emission devices, owing to their unique properties. Here, we integrated the perovskite quantum dot film together with 3D reconfigurable photonic crystals (PCs) to form quantum dot/photonic crystal heterostructures and investigated their interactions at their interfaces. The photonic bandgaps of the presented 3DPCs can be dynamically tuned by heating and applying external mechanical forces, and they can be stably fixed in the intermediate states. By tuning the photonic bandgaps of the 3DPCs, a maximum photoluminescence (PL) enhancement of 11 times that of CsPb(I/Br)3 quantum dots has been achieved. It has been revealed that the combined effects of increased density of photon states and the greatly confined and enhanced electric field on the upper surface of 3DPCs contribute to the enhanced Purcell effect, which in turn leads to the enhanced photoluminescence.

Inhibited Degradation of Organic–Inorganic Perovskite-Based Quantum Dot Films via Rapid Annealing Temperatures

General hot-plate heating is used to form a crystal structure of films; however, how to achieve a homogeneous and regulated crystal formation will be a crucial challenge in the future. In this study, based on perovskite-series materials, organic methylamine lead trioxide (MAPbI3) films doped with inorganic lead iodide (CsPbI3) quantum dots (QDs) are treated using the rapid thermal annealing (RTA) process in argon gas to break the crystallization barrier. These RTA-treated perovskite quantum dot (PQD) films at various temperatures of 100–160 °C are detected using X-ray diffraction, X-ray spectroscopy, and absorbance measurements to investigate their structural and optical properties as well as their binding states. The experimental results demonstrate that the PQD film annealed at 120 °C has optimized characteristics, revealing better crystallinity and the lowest content of oxygen atoms (31.4%) and C-O-C bonding (20.1%). A too-high RTA temperature, more than 140 °C, causes severe degradation with the existence of PbI2. A proper RTA process, an alternative to normal heating and annealing, can effectively inhibit the occurrence of degradation and even usefully improve the performance of PQD films.

Substrate and Excitation Intensity Dependence of Saturable Absorption in Perovskite Quantum Dot Films.

Saturable absorption in perovskite quantum dot (PQD) films, leading to saturation in photoluminescence (PL), is reported. PL of drop-casting films was used to probe how excitation intensity and host-substrate influence the growth of PL intensity. The PQD films were deposited on single-crystal GaAs, InP, Si wafers and glass. Saturable absorption was confirmed through PL saturation in all films, with different excitation intensity thresholds, suggesting strong substrate-dependent optical properties, resulting from absorption nonlinearities in the system. The observations extend our former studies (Appl. Phys. Lett., 2021, 119, 19, 192103), wherein we pointed out that the PL saturation in QDs can be used to create all-optical switches in combination with a bulk semiconductor host.

Hybrid Interfacial Engineering: An Enabling Strategy for Highly Sensitive and Stable Perovskite Quantum Dots/Organic Heterojunction Phototransistors

All-inorganic lead halide perovskite quantum dots (PQD) have attracted tremendous research interest in the field of phototransistors due to their excellent optoelectronic properties. However, the inefficient charge transport/extraction and high trap-state density of the assembled PQD films seriously limit the photoresponsivity of PQD-based phototransistors. Herein, we demonstrate that these limits can be overcome by adopting a novel device architecture composed of a polar-polymer capping layer on a PQD/organic semiconductor (OSC) heterojunction. The polar polymer film plays the role of both electron trapping and encapsulation, whereas OSC provides the fast transport tracks for charges and PQD serves as the photoactive materials. Owing to the balanced dynamic processes of photogenerated charges, highly sensitive photodetection is achieved, as demonstrated by the peak photosensitivity of 1.5 × 104, a photoresponsivity of 2.1 × 104 A/W, a detectivity of 1 × 1015 Jones, and a high gain of 6.4 × 104 under weak incident light of 3 μW/cm2. Additionally, the phototransistors exhibit superior stability and reproducibility with negligible changes in the output current both in darkness and under illumination after storing for 4 months. The results demonstrate the promising potentials of the polar polymer/PQD/OSC heterojunction for high-performance photodetectors, and the mechanism and strategy described here can be applied to other kinds of quantum dots-based optoelectronic devices.