Low Cost, Light Weight SOlar Modules Based on Organic Photovoltaic Technology

Objectives - In order to produce solar modules for rooftop applications the performance and the lifetime must be improved to 5% - 7% and >10 year life. Task 1 Stability - (1) Flexible modules are stable to 1000 hrs at 65 C/85%RH, (2) Flexible modules in glass are stable to >2000 hrs at 85 C/85%RH (no decrease in performance); (3) Adhesive + filler helps stabilize modules; and (4) Solution coatable barriers exhibit good WVTR; work in-progress. Task 2 Performance: n-type charge carriers - (1) N-type polymers could not be synthesized; and (2) More than 30 fullerene derivatives synthesized and tested, Several deep LUMO derivatives accept charge from deep LUMO polymers, higher voltage observed, Improvement in cell efficiency not observed, morphology problem. Task 3 Performance: grid electrode - (1) Exceeded flatness and roughness goals; (2) Exceeds sheet resistance goals; (3) Achieved %T goals; and (4) Performance equivalent to ITO - 2% Efficiency ( av.); work in-progress

Reliable operation of Cr2_2O3_3:Mg/ β\beta-Ga2_2O3_3 p-n heterojunction diodes at 600∘^\circC

$\beta$-Ga$_2$O$_3$-based semiconductor heterojunctions have recently demonstrated improved performance at high voltages and elevated temperatures and are thus promising for applications in power electronic devices and harsh-environment sensors. However, the long-term reliability of these ultra-wide band gap (UWBG) semiconductor devices remains barely addressed and may be strongly influenced by chemical reactions at the p-n heterojunction interface. Here, we experimentally demonstrate operation and evaluate the reliability of Cr$_2$O$_3$:Mg/ $\beta$-Ga$_2$O$_3$ p-n heterojunction diodes at during extended operation at 600$^\circ$C, as well as after 30 repeated cycles between 25-550$^\circ$C. The calculated pO2-temperature phase stability diagram of the Ga-Cr-O material system predicts that Ga$_2$O$_3$ and Cr$_2$O$_3$ should remain thermodynamically stable in contact with each other over a wide range of oxygen pressures and operating temperatures. The fabricated Cr$_2$O$_3$:Mg / $\beta$-Ga$_2$O$_3$ p-n heterojunction diodes show room-temperature on/off ratios >10$^4$ at $\pm$5V and a breakdown voltage (V$_{Br}$) of -390V. The leakage current increases with increasing temperature up to 600$^\circ$C, which is attributed to Poole-Frenkel emission with a trap barrier height of 0.19 eV. Over the course of a 140-hour thermal soak at 600$^\circ$C, both the device turn-on voltage and on-state resistance increase from 1.08V and 5.34 m$\Omega$-cm$^2$ to 1.59V and 7.1 m$\Omega$-cm$^2$ respectively. This increase is attributed to the accumulation of Mg and MgO at the Cr$_2$O$_3$/Ga$_2$O$_3$ interface as observed from TOF-SIMS analysis. These findings inform future design strategies of UWBG semiconductor devices for harsh environment operation and underscore the need for further reliability assessments for $\beta$-Ga$_2$O$_3$ based devices.Comment: 17 pages, 4 figure

Ultrathin Stable Ohmic Contacts for High-Temperature Operation of β\beta-Ga2_2O3_3 Devices

Beta gallium oxide ($\beta$-Ga$_2$O$_3$) shows significant promise in the high-temperature, high-power, and sensing electronics applications. However, long-term stable metallization layers for Ohmic contacts at high temperature present unique thermodynamic challenges. The current most common Ohmic contact design based on 20 nm of Ti has been repeatedly demonstrated to fail at even moderately elevated temperatures (300-400$^{\circ}$C) due to a combination of non-stoichiometric Ti/Ga$_2$O$_3$ interfacial reactions and kinetically favored Ti diffusion processes. Here we demonstrate stable Ohmic contacts for Ga$_2$O$_3$ devices operating up to 500-600$^{\circ}$C using ultrathin Ti layers with a self-limiting interfacial reaction. The ultrathin Ti layer in the 5nm Ti / 100nm Au contact stack is designed to fully oxidize while forming an Ohmic contact, thereby limiting both thermodynamic and kinetic instability. This novel contact design strategy results in an epitaxial conductive anatase titanium oxide interface layer that enables low-resistance Ohmic contacts that are stable both under long-term continuous operation (>500 hours) at 600$^{\circ}$C in vacuum ($\leq$ 10$^{-4}$ Torr), as well as after repeated thermal cycling (15 times) between room temperature and 550$^{\circ}$C in flowing N$_2$. This stable Ohmic contact design will accelerate the development of high-temperature devices by enabling research focus to shift towards rectifying contacts and other interfacial layers.Comment: 25 Pages, 7 Figure

Does Gambling-Focused Treatment Affect Mental Health and Quality of Life? A Systematic Review and Meta-Analysis

Abstract: Cognitive-behavioral (CB) techniques have received substantial empirical support for reducing gambling disorder symptoms and behavior. What has not been established is whether gambling-focused treatment reduces psychological problems and improves quality of life. Individuals experiencing gambling-related harms report that sustained recovery involves changing both gambling behaviors and psychological problems and building a meaningful life. The current systematic review and meta-analysis aimed to examine the effect of CB techniques targeting gambling harms on nontargeted outcomes such as psychological problems and quality of life. Following PRISMA guidelines, a systematic article search was conducted to locate published studies of randomized controlled trials of CB techniques targeting gambling harms and reporting nontargeted outcomes. Random effects meta-analysis was used to quantify the effect of CB techniques on nontargeted outcomes. Ten studies representing 797 participants were included. Eight studies reported the effect of CB techniques on anxiety, 8 on depression, 3 on substance use, and 7 on quality of life. CB techniques significantly reduced anxiety (g = -0.44), depression (g = -0.35), gambling frequency (g = -0.30), and gambling intensity (g = -0.36) at posttreatment, but not substance use. CB techniques also significantly improved quality of life (g = 0.39) at posttreatment. Implications: The targeted reduction of gambling harms may serve as a mechanism of change for reducing psychological problems and improving quality of life. Future studies should employ longitudinal designs to understand the associations between gambling reductions and changes in nontargeted recovery outcomes over time

Harnessing non-stoichiometry and disorder in thermoelectric materials

Thermoelectric materials require an exquisite balancing of thermal and electronic transport properties. Core to achieving such a balance in thermoelectric materials is the pursuit of non-stoichiometric compositions. Non-stoichiometry serves to control the charge carrier concentration, alter the electronic structure, control electron and phonon scattering, and produce anomalies in the phononic structure. As such, the optimized material is far removed from the original parent compound. Looking to the future, a deeper understanding of non-stoichiometry and its impact on electronic and phononic transport is critical to designing the next generation of thermoelectric materials. To convey the importance of non-stoichiometry in thermoelectric materials, we will begin with two classic case examples that highlight how non-stoichiometry profoundly alters transport in thermoelectric materials. These include (i) the alteration of the electronic structure through resonant states in PbTe and (ii) alteration to phonon transport via ‘rattling’ modes in skutterudite compounds. With this foundation, we discuss our recent efforts to control transport in pnictide and chalcogenide compounds through a combination of first principles calculations of defect structures, combinatorial growth of alloys, and bulk synthesis. For example, Figure 1 highlights how first principles calculations can offer insight into native defect populations and their impact on electronic structure. Strategies to accelerate discovery in this high dimensional phase space and critical challenges that remain serve to conclude this discussion of thermoelectric materials. Please click Additional Files below to see the full abstract

Power supply for battery charging

В системах энергоснабжения космических аппаратов очень много внимания уделяется системам заряда аккумуляторных батарей. В состав данных систем входят фотоэлектрические преобразователи, преобразующие энергию солнца в электрический ток. Данные преобразователи имеют крайне низкие энергетические показатели. Предлагаемая работа направлена на повышение эффективности заряда аккумуляторных батарей, посредством применения резонансного инвертора.In the space power systems, much attention is paid to battery charging systems. The composition of these systems includes photoelectric converters that convert the energy of the sun into electric current. These converters have extremely low energy performance. The proposed paper is aimed at increasing the efficiency of batteries chargers, by applying a resonant inverter

Developing new functional TCs

Transparent Conductors (TCs) are increasingly critical to the performance and reliability of a number of technologies. Traditionally based primarily on oxides of Ga, In, Zn and Sn the class is rapidly expanding into new materials including both other oxides and more recently composites of metallic or carbon nanowires. Many of these materials offer unique functionality as well as processing and reliability advantages over some of the historic materials. These compounds are all classically non-stoiciometric and often metastable consisting of oxide, non-oxide and composite materials which are being collectively looked at for an increasingly broad set of applications including photovoltaics, solid state lighting, power electronics and a broad class of flexible and wearable electronics. In this talk, we will focus on two main areas; the development of predictive models to be able to identify dopants and the processing regimes where they can be activated as well as the use of nanowire oxide composites to develop a new generation of tunable high performance TC. The complex set of demands for a desired TC include not only classical performance, but also processibility, cost and reliability necessitating a search for new materials. The ability to use materials genomics to identify new dopable TC materials that are experimentally realizable is rapidly increasing. We will discuss recent work on predicting the dopability of Ga2O3 films, which potentially have broad applicability as buffer layers, TCOs, and in power electronics if the doping level can be well controlled. We will discuss the theoretical predictions for the process windows to activate both Sn and Si as dopants and compare this to experimental results and the literature. We will also present resent results on the theoretical prediction and realization of a new p-type TC based on CuZnS, which has demonstrated conductivities of up to 100 S/cm. The latter while not classically an oxide is certainly non-stoichiometric and properties are enhanced in many cases by the use of complex oxide, sulfide and selenide materials. Together these will illustrate the evolving tools both theory and experiment to develop and realize dopants in wide band gap materials. In cases where single materials may not be sufficient, nanowire (metal or carbon based) composites with oxides is increasingly attractive. For example, Ag, and potentially Cu, nanowires embedded in a metal oxide matrix can potentially produce TCs that can be processed at low temperature, have conductivity and transparency comparable to the best TCOs, control interface stability and electronic properties and are suitable to flexible electronics. We will present work on ZnO, InZnO and ZnSnO composites with Ag nanowires where the performance can be as good as high quality InSnO with films Rs\u3c 10 Ohms/sq. We will discuss the dependence on the interrelationship between the nanowire properties and the oxide properties. We will also discus the concept of employing sandwich oxides to separately optimize the top and bottom interfacial properties. This work was supported, in part, by the Center for the Next Generation of Materials by Design, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. This research also supported in part by the Solar Energy Research Institute for India and the U.S. (SERIIUS) funded jointly by the U.S. Department of Energy subcontract DE AC36-08G028308 (Office of Science, Office of Basic Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology Program, with support from the Office of International Affairs) and the Government of India subcontract IUSSTF/JCERDC-SERIIUS/2012 dated 22nd Nov. 2012

Solar thermoelectricity Via Advanced Latent Heat Storage

An aspect of the present disclosure is a system that includes a thermal valve having a first position and a second position, a heat transfer fluid, and an energy converter where, when in the first position, the thermal valve prevents the transfer of heat from the heat transfer fluid to the energy converter, and when in the second position, the thermal valve allows the transfer of heat from the heat transfer fluid to the energy converter, such that at least a portion of the heat transferred is converted to electricity by the energy converter