Fully spray-coated triple-cation perovskite solar cells

We use ultrasonic spray-coating to sequentially deposit thin films of tin oxide, a triple-cation perovskite and spiro-OMeTAD, allowing us fabricate perovskite solar cells (PSCs) with a champion reverse scan power conversion efficiency (PCE) of 19.4% on small-area substrates. We show that the use of spray-deposition permits us to rapidly (>80 mm s−1) coat 25 mm × 75 mm substrates that were divided into a series of devices each with an active area of 15.4 mm2, yielding an average PCE of 10.3% and a peak PCE of 16.3%. By connecting seven 15.4 mm2 devices in parallel on a single substrate, we create a device having an effective active area of 1.08 cm2 and a PCE of 12.7%. This work demonstrates the possibility for spray-coating to fabricate high efficiency and low-cost perovskite solar cells at speed

Degradation of Hydrophobic, Anti-Soiling Coatings for Solar Module Cover Glass

Soiling of solar module cover glass is a serious problem for solar asset managers. It causes a reduction in power output due to attenuation of the incident light, and reduces the return on investment. Regular cleaning is required to mitigate the effect but this is a costly procedure. The application of transparent hydrophobic, anti-soiling coatings to the cover glass is a promising solution. These coatings have low surface energy and contaminants do not adhere well. Even if soiling does remain on the coated surface, it is much more easily removed during cleaning. The performance of the coatings is determined using the water contact angle and roll-off angle measurements. However, although hydrophobic coatings hold out great promise, outdoor testing revealed degradation that occurs surprisingly quickly. In this study, we report on results using laboratory-based damp heat and UV exposure environmental tests. We used SEM surface imaging and XPS surface chemical analysis to study the mechanisms that lead to coating degradation. Loss of surface fluorine from the coatings was observed and this appeared to be a major issue. Loss of nanoparticles was also observed. Blistering of surfaces also occurs, leading to loss of coating material. This was probably due to the movement of retained solvents and was caused by insufficient curing. This mechanism is avoidable if care is taken for providing and carrying out carefully specified curing conditions. All these symptoms correlate well with observations taken from parallel outdoor testing. Identification of the mechanisms involved will inform the development of more durable anti-soiling, hydrophobic coatings for solar application

An innovative approach for fabrication of Cu2ZnSnSe4 absorber layers using solutions of elemental metal powders

An innovative approach has been demonstrated for the deposition of Cu2ZnSnSe4 (CZTSe) absorber layers. Using a unique, safe solvent combination, moving away from hydrazine, elemental Cu, Zn, Sn and S/Se can be fully dissolved at ambient conditions, with the composition easily controlled. The preparation and the spray deposition of these solutions are performed in air, allowing a quick, easy and inexpensive process. Upon selenisation, large crystals are observed which are identified as the CZTSe kesterite phase using X-ray diffraction and Raman, the latter showing no distinctive signs of any binary or ternary secondary phases. Using this method, CZTSe absorber layers have been prepared for use in thin-film solar cells reaching efficiency of 3.2%. With further device optimisation, improved device performance will be achieved. © 2017 The Author

An innovative approach for fabrication of Cu2ZnSnSe4 absorber layers using solutions of elemental metal powders

An innovative approach has been demonstrated for the deposition of Cu2ZnSnSe4 (CZTSe) absorber layers. Using a unique, safe solvent combination, moving away from hydrazine, elemental Cu, Zn, Sn and S/Se can be fully dissolved at ambient conditions, with the composition easily controlled. The preparation and the spray deposition of these solutions are performed in air, allowing a quick, easy and inexpensive process. Upon selenisation, large crystals are observed which are identified as the CZTSe kesterite phase using X-ray diffraction and Raman, the latter showing no distinctive signs of any binary or ternary secondary phases. Using this method, CZTSe absorber layers have been prepared for use in thin-film solar cells reaching efficiency of 3.2%. With further device optimisation, improved device performance will be achieved. © 2017 The Author

Development of ZnTe as a back contact material for thin film cadmium telluride solar cells

This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution 4.0 Licence (CC BY). Full details of this licence are available at http://creativecommons.org/licenses/by/4.0/Cadmium telluride (CdTe) is high-efficiency commercialised thin film photovoltaic technology. However, developing a stable low-resistivity back contact to the CdTe solar cells is still an issue. High work function and low level of doping of this material don't allow to create an ohmic contact with metals directly. Copper is commonly used to lower the back contact barrier in CdTe solar cells, but an excessive amount of copper diffusing through the cell is harmful for the device performance and stability. In this work a copper-doped ZnTe (ZnTe:Cu) buffer layer was incorporated in between CdTe and gold metal contact by high-rate pulsed DC magnetron sputtering. The back contact was then activated by rapid thermal processing (RTP) resulting in spectacular improvement in key device performance indicators, open circuit voltage (VOC) and fill factor (FF)

Solution processing of CuIn(S,Se) 2 and Cu(In,Ga)(S,Se) 2 thin film solar cells using metal chalcogenide precursors

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).In order to realize the true low cost potential of Cu(In,Ga)(S,Se)2 (CIGS) thin film solar cells, high performance needs to be combined with simple and easily controllable atmospheric-based deposition processes. A molecular solution-based approach for CIGS deposition is proposed, using metal chalcogenide precursors dissolved in an amine-thiol solvent combination. CIGS thin films were sprayed with varying Ga content and the sprayed films were incorporated into solar cells. The effect of the Ga content on the material and device properties is investigated. A champion power conversion efficiency of 9.8% (active area) was achieved, which highlights the potential of this methodology

Systems Biology of Free Radicals and Antioxidants

Book chapterThe South African fynbos plant, Aspalathus linearis (Brum.f) Dahlg. (Fabaceae, Tribe Crotalarieae), is traditionally used as a herbal tisane referred to as rooibos or redbush. This plant has claimed medicinal properties based mostly on anecdotal evidence. Rooibos is naturally caffeine free and contains a unique blend of polyphenolic compounds. Based on its in vitro antioxidant potential, a few studies also suggest modulation of oxidative stress/damage by rooibos extracts in experimental animals. More recent studies have examined the bioactivity of rooibos in humans. Together, these factors have contributed to the popularity of this herbal tea as a health beverage, both locally and internationally. This chapter focuses on the in vitro antioxidant activity of rooibos and discusses recent animal and human studies