Dual-functioning displays, which can simultaneously transmit and receive information and energy through visible light, would enable enhanced user interfaces and device-to-device interactivity. We ...demonstrate that double heterojunctions designed into colloidal semiconductor nanorods allow both efficient photocurrent generation through a photovoltaic response and electroluminescence within a single device. These dual-functioning, all-solution-processed double-heterojunction nanorod light-responsive light-emitting diodes open feasible routes to a variety of advanced applications, from touchless interactive screens to energy harvesting and scavenging displays and massively parallel display-to-display data communication.
Scalable and cost-effective protocols to pattern and integrate colloidal quantum dots (QDs) with high resolution have been challenging to establish. While their solubility can facilitate certain ...processes such as spin-casting into thin films, it also makes them incompatible with many conventional patterning techniques including photolithography that require solution processing. In this work, we present “photoresist (PR) contact patterning”, a dry means to pattern QD films over large areas with high resolution while maintaining desired properties. Here, a PR layer on an elastomer substrate is patterned by conventional photolithography and used as a dry contact stamp to selectively peel off QDs in the contact regions, leaving behind a QD film with the negative of the PR pattern. Once patterned, QD films are readily transferred and integrated on foreign substrates by subsequent transfer printing processes. Patterned PR layers can also be transferred from elastomer substrates onto QD films and used as masking layers for subsequent deposition and patterning of additional materials, e.g., patterned metal electrodes or charge transport layers for QD-based devices. The study of the interfacial mechanics and energy of materials associated with PR contact patterning reveals why a lithographically patterned PR is superior for high-resolution QD film patterning. Applicability of PR contact patterning is demonstrated through the fabrication of red, green, and blue (RGB) QD light-emitting diode pixels. PR contact patterning presented in this work not only allows dry patterning of QD films but also enables high-resolution integration of functional multistack structures for future QD-based electronic and optoelectronic devices.
CdSe/CdTe heterojunction nanorods with type II staggered band offset can allow directional and efficient separation of photogenerated charge carriers. However, CdTe nanocrystals can often be easily ...oxidized even with postsynthesis processing in air, which can then lead to charge traps that negate the benefits of the type II band offset. Here, we introduce a simple ligand exchange method to replace the native ligands on CdSe/CdTe heterojunction nanorods with 1-octanethiol resulting in improved photoluminescence and good stability in air. Transient absorption measurements reveal that electron transfer from CdTe to CdSe remains efficient/fast (∼400 fs) despite the hole trapping nature of thiol ligands for CdSe. Absorption bleach arising from CdTe-to-CdSe electron transfer can be observed out to 1 μs even after days of storage in air, an order of magnitude longer than heterojunction nanorods with native ligands that are processed with anhydrous solvents under air-free conditions and kept air-free. This improved stability/robustness that preserves efficient charge separation translates to enhanced photocurrent generation especially with respect to contribution from photoexcitation of CdTe transitions.
Composition variation and formation of core/shell heterostructures have allowed the extension and applicability of size-tunable optical properties of colloidal semiconductor nanocrystals. Anisotropic ...shapes such as nanorods (NRs) provide new and further refined properties but relatively simple and empowering approaches such as alloying and controlled heterostructure formation are much more challenging to apply to these materials. Here, we start from a well-defined CdS/CdSe barbell-shaped NR heterostructure and perform sequential cation exchanges first with Cu and then with Cd/Zn under relatively mild conditions to achieve alloying while preserving the structure. By using a mixture of Cd and Zn in the presence of a thiol, controllable amounts of alloying in both components could be achieved. Growth of a final ZnSe shell enhances the photoluminescence and allows the creation of a series of double-heterojunction NRs with emission spanning the visible spectral range.
Here, we report the successful application of core/patchy-shell CdSe/CdSe x Te1–x type-II heterojunction nanorods (HNRs) to realize efficient sensitized solar cells. The core/patchy-shell structure ...designed to have a large type-II heterointerface without completely shielding the CdSe core significantly improves photovoltaic performance compared to other HNRs with minimal or full-coverage shells. In addition, cosensitization with CdS grown by successive ionic layer adsorption and reaction further improves the power conversion efficiency. One-diode model analysis reveals that the HNRs having exposed CdSe cores and suitably grown CdS result in significant reduction of series resistance. Investigation of the intercorrelation between diode quality parameters, diode saturation current density (J 0) and recombination order (β = (ideality factor)−1) reveals that HNRs with open CdSe cores exhibit reduced recombination. These results confirm that the superior performance of core/patchy-shell HNRs results from their fine-tuned structure: photocurrent is increased by the large type-II heterointerface and recombination is effectively suppressed due to the open CdSe core enabling facile electron extraction. An optimized power conversion efficiency of 5.47% (5.89% with modified electrode configuration) is reported, which is unmatched among photovoltaics utilizing anisotropic colloidal heterostructures as light-harvesting materials.
Semiconductor sensitized solar cells, a promising candidate for next-generation photovoltaics, have seen notable progress using 0-D quantum dots as light harvesting materials. Integration of ...higher-dimensional nanostructures and their multi-composition variants into sensitized solar cells is, however, still not fully investigated despite their unique features potentially beneficial for improving performance. Herein, CdSe/CdSe(x)Te(1-x) type-II heterojunction nanorods are utilized as novel light harvesters for sensitized solar cells for the first time. The CdSe/CdSe(x)Te(1-x) heterojunction-nanorod sensitized solar cell exhibits ~33% improvement in the power conversion efficiency compared to its single-component counterpart, resulting from superior optoelectronic properties of the type-II heterostructure and 1-octanethiol ligands aiding facile electron extraction at the heterojunction nanorod-TiO(2) interface. Additional ~31% enhancement in power conversion efficiency is achieved by introducing percolation channels of large pores in the mesoporous TiO(2) electrode, which allow 1-D sensitizers to infiltrate the entire depth of electrode. These strategies combined together lead to 3.02% power conversion efficiency, which is one of the highest values among sensitized solar cells utilizing 1-D nanostructures as sensitizer materials.
One-dimensionally elongated nanoparticles with type-II staggered band offset are of potential use as light-harvesting materials for photovoltaics, but only a limited attention has been given to ...elucidate the factors governing the cell performance obtainable from such materials. Herein, we describe a combined strategy to enhance charge collection from CdSe/CdSexTe1-x type-II heterojunction nanorods (HNRs) utilized as light harvesters for sensitized solar cells. By integrating morphology- and composition-tuned type-II HNRs into solar cells, factors that yield interfaces favorable both for the electron injection into TiO2 and hole transfer to electrolyte are examined. Furthermore, it is shown that a more efficient photovoltaic system results from cosensitization with CdS quantum dots (QDs) predeposited on a TiO2 scaffold, which improves charge collection from HNRs. Electrochemical impedance spectroscopy (EIS) analysis suggests that such a synergistically enhanced system benefits from the decreased recombination within HNRs and facilitated charge transport through the cosensitized TiO2 electrode, even with the activation of a recombination path presumably related to the photogenerated holes in CdS QDs.
Mutations in the KATP channel genes, ABCC8 and KCNJ11, are the most common cause of congenital hyperinsulinism. The diagnosis of KATP-hyperinsulinism is important for the clinical management of the ...condition. We aimed to determine the clinical features that help to identify KATP-hyperinsulinism at diagnosis.
We studied 761 individuals with KATP-hyperinsulinism and 862 probands with hyperinsulinism of unknown aetiology diagnosed before 6 months of age. All were referred as part of routine clinical care.
We compared the clinical features of KATP-hyperinsulinism and unknown hyperinsulinism cases. We performed logistic regression and receiver operator characteristic (ROC) analysis to identify the features that predict KATP-hyperinsulinism.
Higher birth weight, diazoxide unresponsiveness and diagnosis in the first week of life were independently associated with KATP-hyperinsulinism (adjusted odds ratio: 4.5 (95% CI: 3.4-5.9), 0.09 (0.06-0.13) and 3.3 (2.0-5.0) respectively). Birth weight and diazoxide unresponsiveness were additive and highly discriminatory for identifying KATP-hyperinsulinism (ROC area under the curve for birth weight 0.80, diazoxide responsiveness 0.77, and together 0.88, 95% CI: 0.85-0.90). In this study, 86% born large for gestation and 78% born appropriate for gestation and who did not respond to diazoxide treatment had KATP-hyperinsulinism. In contrast, of those individuals born small for gestation, none who were diazoxide responsive and only 4% of those who were diazoxide unresponsive had KATP-hyperinsulinism.
Individuals with hyperinsulinism born appropriate or large for gestation and unresponsive to diazoxide treatment are most likely to have an ABCC8 or KCNJ11 mutation. These patients should be prioritised for genetic testing of KATP channel genes.
One-dimensionally elongated nanoparticles with type-II staggered band offset are of potential use as light-harvesting materials for photovoltaics, but only a limited attention has been given to ...elucidate the factors governing the cell performance obtainable from such materials. Herein, we describe a combined strategy to enhance charge collection from CdSe/CdSe
Te
type-II heterojunction nanorods (HNRs) utilized as light harvesters for sensitized solar cells. By integrating morphology- and composition-tuned type-II HNRs into solar cells, factors that yield interfaces favorable both for the electron injection into TiO
and hole transfer to electrolyte are examined. Furthermore, it is shown that a more efficient photovoltaic system results from cosensitization with CdS quantum dots (QDs) predeposited on a TiO
scaffold, which improves charge collection from HNRs. Electrochemical impedance spectroscopy (EIS) analysis suggests that such a synergistically enhanced system benefits from the decreased recombination within HNRs and facilitated charge transport through the cosensitized TiO
electrode, even with the activation of a recombination path presumably related to the photogenerated holes in CdS QDs.
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