Flexible copper-indium-diselenide films and devices for space applications

With the ever increasing demands on space power systems, it is imperative that low cost, lightweight, reliable photovoltaics be developed. One avenue of pursuit for future space power applications is the use of low cost, lightweight flexible PV cells and arrays. Most work in this area assumes the use of flexible amorphous silicon (a-Si), despite its inherent instability and low efficiencies. However, polycrystalline thin film PV such as copper-indium-diselenide (CIS) are inherently more stable and exhibit better performance than a-Si. Furthermore, preliminary data indicate that CIS also offers exciting properties with respect to space applications. However, CIS has only heretofore only produced on rigid substrates. The implications of flexible CIS upon present and future space power platforms was explored. Results indicate that space qualified CIS can dramatically reduce the cost of PV, and in most cases, can be substituted for silicon (Si) based on end-of-life (EOL) estimations. Furthermore, where cost is a prime consideration, CIS can become cost effective than gallium arsenide (GaAs) in some applications. Second, investigations into thin film deposition on flexible substrates were made, and data from these tests indicate that fabrication of flexible CIS devices is feasible. Finally, data is also presented on preliminary TCO/CdS/CuInSe2/Mo devices

Status of flexible CIS research at ISET

Polycrystalline thin film solar cells fabricated on light-weight, flexible substrates are very attractive for space applications. In this work CulnSe2 (CIS) based thin film devices were processed on metallic foil substrates using the selenization technique. CIS deposition method involved reaction of electron-bean evaporated Cu-In precursor layers with a selenizing atmosphere at around 400 C. Several metallic foils such as Mo, Ti, Al, Ni, and Cu were evaluated as possible substrates for these devices. Solar cells with AM1.5 efficiencies of 9.0-9.34 percent and good mechanical integrity were demonstrated on Mo and Ti foils. Monolithic integration of these devices was also demonstrated up to 4 in x 4 in size

Efficient CuInSe 2 Solar Cells Fabricated by a Novel Ink Coating Approach

A novel technique is developed for the deposition of CuInSe 2 (CIS) thin films for solar cell applications. The technique uses an ink formulation that contains Cu-In metallic pigments. A precursor layer is first formed coating this ink onto the selected substrate. The precursor film is then reacted with Se to form the CIS compound. Solar cells were fabricated on CIS absorber layers prepared by this low cost ink coating approach and devices with a conversion efficiency of over 9.0% were demonstrated. © 1998 The Electrochemical Society. S1099-0062(98)08-063-8. All rights reserved. Manuscript submitted August 14, 1998; revised manuscript received September 9, 1998. Available electronically October 1, 1998. Group I-III-VI materials are considered to be highly promising as absorber layers in high-efficiency thin film solar cell structures. In fact, the highest efficiency thin film device to date was produced on a Cu(In,Ga)Se 2 (CIGS) absorber film grown by a vacuum evaporation technique. The demonstrated conversion efficiency of 17.7% confirmed the capability of this material to yield highly efficient active devices when employed in thin film solar cell structures. High-efficiency solar cells have commonly been fabricated on CuInSe 2 (CIS) or CIGS absorbers deposited by costly vacuum deposition techniques such as coevaporation 1 and two-stage processes utilizing evaporation or sputtering. 2 There is presently great interest in the development of new lower cost processing methods for the growth of high quality CIS-type absorbers for thin film solar cell applications. Slurry or ink deposition by large area nonvacuum coating methods such as screen printing, spraying, curtain coating, roll coating, or doctor blading are attractive low-cost approaches for the growth of thin film solar cell absorbers, provided that the precursor layers obtained by these deposition techniques can be converted into high quality semiconductor films that are required for solar cell fabrication. There have been several attempts to deposit CIS absorbers using the screen printing technique. For example, Arita et al. described a method that involved (i) mixing pure Cu, In, and Se powders in the compositional ratio of 1:1:2, (ii) milling these powders in a ball mill and forming a screen printable paste, (iii) screen printing the paste on a substrate, and (iv) sintering this precursor film to form the compound layer. As can be seen from the review of previous work, the nature of the ingredients in the formulation of a paste or an ink is very important for the formation of a precursor layer which can later be converted into a high quality CIS-type compound film with properties that are desirable for solar cell applications. In this article we report a low-cost ink coating technique that was successfully employed for the deposition of CIS absorbers that could be used for the fabrication of over 9% efficient thin film solar cells. Experimental The general steps of the low-cost process used in this work for the growth of thin film CIS absorbers are schematically shown in The source of Cu and In in this work was a Cu-In alloy powder with a preselected and fixed Cu/In stoichiometric ratio. The Cu-In alloy powder was obtained by the melt atomization technique. To prepare the powder, 99.99% pure Cu and 99.99% pure In were melted under a hydrogen curtain at above 900°C. The Cu/In ratio of the melt corresponded to the targeted value range of 0.87-0.9. The melted alloy was transformed into powder in a gas atomizer employing Ar as the quenching gas. Quenched powder was collected at the bottom of the reactor and sieved to separate the particles that were smaller than 20 µm in size which were used in this work as the pigment. About 10 g of the Cu-In pigment was mixed with 23 g of water. A small amount (about 1.5 wt %) of a wetting agent and dispersant were added to this aqueous formulation. The mixture was milled in a ball mill for 42 h. The resulting metallic ink was water-thin. Particle size analysis was done on a sample of this ink using

Fluorine-induced improvement of structural and optical properties of CdTe thin films for solar cell efficiency enhancement

CdTe thin films of different thicknesses were electrodeposited and annealed in air after different chemical treatments to study the effects of thickness and the different chemical treatments on these films for photovoltaic applications. The thicknesses of the samples range from 1.1 μm to 2.1 μm and the annealing process was carried out after prior CdCl2 treatment and CdCl2+CdF2 treatment as well as without any chemical treatment. Detailed optical and structural characterisation of the as-deposited and annealed CdTe thin films using UV-Vis spectrophotometry and x-ray diffraction reveal that incorporating fluorine in the well-known CdCl2 treatment of CdTe produces remarkable improvement in the optical and structural properties of the materials. This CdCl2+CdF2 treatment produced solar cell with efficiency of 8.3% compared to CdCl2 treatment, with efficiency of 3.3%. The results reveal an alternative method of post-deposition chemical treatment of CdTe which can lead to the production of CdTe-based solar cells with enhanced photovoltaic conversion efficiencies compared to the use of only CdCl2. Keywords: CdTe; CdCl2

Optimisation of pH of cadmium chloride post-growth-treatment in processing CDS/CDTE based thin film solar cells

The role of Chlorine-based activation in the production of high quality CdS/CdTe photovoltaic have been well discussed and explored with an overlook of the effect of Cadmium chloride (CdCl2) post-growth treatment acidity on the property of the fabricated devices. This work focuses on the optimisation of CdCl2 post-growth treatment pH as it affects both the material and fabricated device properties of all-electrodeposited multilayer glass/FTO/n-CdS/n-CdTe/p-CdTe configuration. CdCl2 treatments with acidity ranging from pH1 to pH4 were explored. The properties of the ensued CdTe layer were explored using optical, morphological, compositional structural and electrical property analysis, while, the effect on fabricated multilayer glass/FTO/n-CdS/n-CdTe/p-CdTe configuration were also explored using both I-V and C-V measurements. Highest improvements in the optical, morphological, compositional and structural were observed at pH2 CdCl2 post-growth treatment with an improvement in absorption edge, grain size, crystallinity and crystallite size. Conductivity type conversions from n-CdTe to p-CdTe, increase in pin-hole density and collapse of the absorption edge were observed after pH1 CdCl2 treatment. The highest fabricated solar cell efficiency of 13% was achieved using pH2 CdCl2 treatment as compared to other pH values explored

Na incorporation in Mo and CuInSe from production processes

Abstract Results of characterization of thin "lms of Mo deposited by DC magnetron sputtering on soda-lime glass (Mo/SLG) and CuInSe (CIS) on Mo/SLG are presented. The primary objective of the work was to clarify the factors determining the concentration of Na in commercial-grade CIS. Mo "lms were deposited by three laboratories manufacturing CIS thin "lm solar cells. Analysis was by secondary ion mass spectrometry, scanning electron microscopy and X-ray di!raction. Changes in Mo deposition parameters in general a!ected the Na level but there was no obvious link to any single Mo deposition parameter. Oxygen content directly a!ected the Na level. The Na behavior was not obviously connected to "lm preferred orientation. Selenization of the Mo layers was also examined. Elemental Se vapor was found to produce signi"cantly less selenization than H Se. The amount of selenization was also strongly dependent upon Mo deposition conditions, although a speci"c source of the change in reaction rate was not found. Na distributions in the CIS deposited on the Mo were not limited by the di!usivity of the Na. The Na concentration in the CIS was increased by annealing the Mo "lms both with and without intentionally added Na. The Na level in the CIS appears to be set more by the CIS deposition process than by the Na concentration in the Mo so long as the Mo contains su$cient Na to 0927-0248/99/$ -see front matter 1999 Published by Elsevier Science B.V. All rights reserved. PII: S 0 9 2 7 -0 2 4 8 ( 9 9 ) 0 0 0 2 6 -4 saturate the available sites in the CIS. 1999 Published by Elsevier Science B.V. All rights reserved

Effects of deposition time and post-deposition annealing on the physical and chemical properties of electrodeposited CdS thin films for solar cell application

CdS thin films were cathodically electrodeposited by means of a two-electrode deposition system for different durations. The films were characterised for their structural, optical, morphological and compositional properties using x-ray diffraction (XRD), spectrophotometry, scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) respectively. The results obtained show that the physical and chemical properties of these films are significantly influenced by the deposition time and post-deposition annealing. This influence manifests more in the as-deposited materials than in the annealed ones. XRD results show that the crystallite sizes of the different films are in the range (9.4 – 65.8) nm and (16.4 – 66.0) nm in the as-deposited and annealed forms respectively. Optical measurements show that the absorption coefficients are in the range (2.7×104 – 6.7×104) cm-1 and (4.3×104 – 7.2×104) cm-1 respectively for as-deposited and annealed films. The refractive index is in the range (2.40 – 2.60) for as-deposited films and come to the value of 2.37 after annealing. The extinction coefficient varies in the range (0.1 – 0.3) in asdeposited films and becomes 0.1 in annealed films. The estimated energy bandgap of the films is in the range (2.48 – 2.50) eV for as-deposited films and becomes 2.42 eV for all annealed films. EDX results show that all the films are S-rich in chemical composition with fairly uniform Cd/S ratio after annealing. The results show that annealing improves the qualities of the films and deposition time can be used to control the film thickness. Keywords: Electrodeposition; two-electrode system; CdS; annealing; deposition time; thin-film

Inoculation theory in the post-truth era: Extant findings and new frontiers for contested science, misinformation, and conspiracy theories

Abstract: Although there has been unprecedented attention to inoculation theory in recent years, the potential of this research has yet to be reached. Inoculation theory explains how immunity to counter‐attitudinal messages is conferred by preemptively exposing people to weakened doses of challenging information. The theory has been applied in a number of contexts (e.g., politics, health) in its 50+ year history. Importantly, one of the newest contexts for inoculation theory is work in the area of contested science, misinformation, and conspiracy theories. Recent research has revealed that when a desirable position on a scientific issue (e.g., climate change) exists, conventional preemptive (prophylactic) inoculation can help to protect it from misinformation, and that even when people have undesirable positions, “therapeutic” inoculation messages can have positive effects. We call for further research to explain and predict the efficacy of inoculation theory in this new context to help inform better public understandings of issues such as climate change, genetically modified organisms, vaccine hesitancy, and other contested science beliefs such as conspiracy theories about COVID‐19

Using social and behavioural science to support COVID-19 pandemic response

The COVID-19 pandemic represents a massive global health crisis. Because the crisis requires large-scale behaviour change and places significant psychological burdens on individuals, insights from the social and behavioural sciences can be used to help align human behavior with the recommendations of epidemiologists and public health experts. Here we discuss evidence from a selection of research topics relevant to pandemics, including work on navigating threats, social and cultural influences on behaviour, science communication, moral decision-making, leadership, and stress and coping. In each section, we note the nature and quality of prior research, including uncertainty and unsettled issues. We identify several insights for effective response to the COVID-19 pandemic, and also highlight important gaps researchers should move quickly to fill in the coming weeks and months