Fabrication of ZnO/Cu<inf>2</inf>O heterojunctions in atmospheric conditions: Improved interface quality and solar cell performance

Zn_1-xMg_xO/Cu_2O heterojunctions were successfully fabricated in open-air at low temperatures via atmospheric atomic layer deposition of Zn_1-xMg_xO on thermally oxidized cuprous oxide. Solar cells employing these heterojunctions demonstrated a power conversion efficiency exceeding 2.2% and an open-circuit voltage of 0.65 V. Surface oxidation of Cu_2O to CuO prior to and during Zn_1-xMg_xO deposition was identified as the limiting factor to obtaining a high quality heterojunction interface. Optimization of deposition conditions to minimize Cu_2O surface oxidation led to improved device performance, tripling the open-circuit voltage and doubling the short-circuit current density. These values are the highest reported for a ZnO/Cu_2O interface formed in air, and highlight atmospheric ALD as a promising technique for inexpensive and scalable fabrication of ZnO/Cu_2O heterojunctions.This is the final published version. It is also available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0927024814005005#

Size-Dependent Photon Emission from Organometal Halide Perovskite Nanocrystals Embedded in an Organic Matrix

10.1021/jz502615eJournal of Physical Chemistry Letters63446-45

Efficient Triplet Exciton Fusion in Molecularly Doped Polymer Light-Emitting Diodes.

Solution-processed polymer organic light-emitting diodes (OLEDs) doped with triplet-triplet annihilation (TTA)-upconversion molecules, including 9,10-diphenylanthracene, perylene, rubrene and TIPS-pentacene, are reported. The fraction of triplet-generated electroluminescence approaches the theoretical limit. Record-high efficiencies in solution-processed OLEDs based on these materials are achieved. Unprecedented solid-state TTA-upconversion quantum yield of 23% (TTA-upconversion reaction efficiency of 70%) at electrical excitation well below one-sun equivalent is observed.D.D. acknowledges the Department of Physics (University of Cambridge) and the KACST–Cambridge University Joint Centre of Excellence for financial support. L.Y. thanks the Singapore Agency for Science, Technology and Research (A*STAR) for a PhD studentship. The authors thank the Engineering and Physical Sciences Research Council (EPSRC) for financial support

Language development after cochlear implantation: an epigenetic model

Growing evidence supports the notion that dynamic gene expression, subject to epigenetic control, organizes multiple influences to enable a child to learn to listen and to talk. Here, we review neurobiological and genetic influences on spoken language development in the context of results of a longitudinal trial of cochlear implantation of young children with severe to profound sensorineural hearing loss in the Childhood Development after Cochlear Implantation study. We specifically examine the results of cochlear implantation in participants who were congenitally deaf (N = 116). Prior to intervention, these participants were subject to naturally imposed constraints in sensory (acoustic–phonologic) inputs during critical phases of development when spoken language skills are typically achieved rapidly. Their candidacy for a cochlear implant was prompted by delays (n = 20) or an essential absence of spoken language acquisition (n = 96). Observations thus present an opportunity to evaluate the impact of factors that influence the emergence of spoken language, particularly in the context of hearing restoration in sensitive periods for language acquisition. Outcomes demonstrate considerable variation in spoken language learning, although significant advantages exist for the congenitally deaf children implanted prior to 18 months of age. While age at implantation carries high predictive value in forecasting performance on measures of spoken language, several factors show significant association, particularly those related to parent–child interactions. Importantly, the significance of environmental variables in their predictive value for language development varies with age at implantation. These observations are considered in the context of an epigenetic model in which dynamic genomic expression can modulate aspects of auditory learning, offering insights into factors that can influence a child’s acquisition of spoken language after cochlear implantation. Increased understanding of these interactions could lead to targeted interventions that interact with the epigenome to influence language outcomes with intervention, particularly in periods in which development is subject to time-sensitive experience

Cost-effectiveness of collaborative care for chronically ill patients with comorbid depressive disorder in the general hospital setting, a randomised controlled trial

Background. Depressive disorder is one of the most common disorders, and is highly prevalent in chronically ill patients. The presence of comorbid depression has a negative influence on quality of life, health care costs, self-care, morbidity, and mortality. Early diagnosis and well-organized treatment of depression has a positive influence on these aspects. Earlier research in the USA has reported good results with regard to the treatment of depression with a collaborative care approach and an antidepressant algorithm. In the UK 'Problem Solving Treatment' has proved to be feasible. However, in the general hospital setting this approach has not yet been evaluated. Methods/Design. CC: DIM (Collaborative Care: Depression Initiative in the Medical setting) is a two-armed randomised controlled trial with randomisation at patient level. The aim of the trial is to evaluate the treatment of depressive disorder in general hospitals in the Netherlands based on a collaborative care framework, including contracting, 'Problem Solving Treatment', antidepressant algorithm, and manual-guided self-help. 126 outpatients with diabetes mellitus, chronic obstructive pulmonary disease, or cardiovascular diseases will be randomised to either the intervention group or the control group. Patients will be included if they have been diagnosed with moderate to severe depression, based on the DSM-IV criteria in a two-step screening method. The intervention group will receive treatment based on the collaborative care approach; the control group will receive 'care as usual'. Baseline and follow-up measurements (after 3, 6, 9, and 12 months) will be performed by means of questionnaires. The primary outcome measure is severity of depressive symptoms, as measured with the PHQ-9. The secondary outcome measure is the cost-effectiveness of these treatments according to the TiC-P, the EuroQol and the SF-36. Discussion. Earlier research has indicated that depressive disorder is a chronic, mostly recurrent illness, which tends to cluster with physical comorbidity. Even though the treatment of depressive disorder based on the guidelines for depression is proven effective, these guidelines are often insufficiently adhered to. Collaborative care and 'Problem Solving Treatment' will be specifically tailored to patients with depressive disorders and evaluated in a general hospital setting in the Netherlands

Engineering schottky contacts in open-air fabricated heterojunction solar cells to enable high performance and ohmic charge transport

The efficiencies of open-air processed Cu2O/Zn1-xMgxO heterojunction solar cells are doubled by reducing the effect of the Schottky barrier between Zn1-xMgxO and the indium tin oxide (ITO) top contact. By depositing Zn1-xMgxO with a long band-tail, charge flows through the Zn1-xMgxO/ITO Schottky barrier without rectification by hopping between the sub-bandgap states. High current densities are obtained by controlling the Zn1-xMgxO thickness to ensure that the Schottky barrier is spatially removed from the p-n junction, allowing the full built-in potential to form, in addition to taking advantage of the increased electrical conductivity of the Zn1-xMgxO films with increasing thickness. This work therefore shows that the Zn1-xMgxO window layer sub-bandgap state density and thickness are critical parameters that can be engineered to minimize the effect of Schottky barriers on device performance. More generally, these findings show how to improve the performance of other photovoltaic system reliant on transparent top contacts, e.g., CZTS and CIGS

Low-temperature open-atmosphere growth of WO<inf>3</inf> thin films with tunable and high-performance photoresponse

Tungsten oxide (WO3), an n-type semiconductor, has many potential applications, e.g., electrochromic devices, photodetectors, photoelectrochemical cells, photocatalysts, supercapacitors, memristors, electrolyte-gated transistors, etc. Most deposition routes of films require either vacuum processes or post-deposition annealing, which is not suitable for many applications. In this work, WO3 thin films are made from a W[CO]6 precursor using atmospheric pressure-spatial chemical vapor deposition (AP-SCVD), without any post-deposition annealing. Films were grown on Si substrates at 320°C and were conformal over cm2 areas, with the film-preferred orientations tuned via control of growth rate. Three exemplar photo-responsive functions with strong performance are demonstrated: water splitting, UV photodetection, and photocatalytic degradation. The strong performance is linked to the highly exothermic reaction which produces crystalline materials at the low deposition temperature as well as control of the film orientation through tuning the film growth rate. Overall, AP-SCVD is shown to have key advantages over other routes for forming WO3 thin films for photo-responsive applications