This paper reviews the status of solar cell technology based on n-type crystalline silicon wafers. It aims to explain the reasons behind the strong and increasing attention for n-type cells, including the inherent advantages of n-type base doping for high diffusion length, and for the industrialization of designs with good rear-side electronic and optical properties. The focus will be on cells using diffused junctions.
Since the 1980s, ethylene-vinyl acetate (EVA) has been the standard encapsulation material for crystalline photovoltaic modules. From a mechanical point of view, the encapsulant takes the function of a compliant buffer layer surrounding the solar cells. Therefore, understanding its complex mechanical properties is essential for a robust module design that withstands thermal and mechanical loads. In the cured state after lamination, its stiffness features a high sensitivity to temperature especially in the glass transition region around -35°C, and a dependence on time which becomes obvious in relaxation and creep behaviour. This paper outlines the viscoelastic properties of EVA and the corresponding standard experimental methods, as well as the impact on the accuracy of wind and snow load test procedures for PV modules.
When Stion started looking for sites to establish its first volume production plant, Mississippi was not even on its radar. After vetting some “100 different opportunities, state and local flavors and locations,” the San Jose-based thin-film PV module company had “narrowed the list down to a half-dozen or so pretty quickly,” including Texas, Virginia, Michigan, and California, according to CEO Chet Farris.
With more than 80% of PV module demand being satisfied by crystalline-based modules, the health of the silicon and wafer supply chain is of vital importance to the overall PV industry. This paper reviews the overall materials value chain from the manufacture of PV silicon to the wafer, prepared for manufacture of the cell. A glimpse is provided of the various market dynamics that exist in the supply chain, as well as the technology trends that influence or threaten the supply of wafers. Although the manufacturing routes are mature and well established, we also take a look at the possibility of novel and disruptive technologies altering the overall supply landscape.
Germany and Italy are forecasted to drive solar demand to new highs in 2011, with rumours of installations up to 22GW on the cards for this year. The German and Italian markets, scheduled to peak in 2011 and 2012, respectively, face a potential problem in terms of where to sell their modules if these two countries cannot accommodate 10GW of installations per year. The emerging markets can solve part of this challenge and will deliver new opportunities to the solar industry. Some Asian, European and Middle Eastern regions will require up to of 6GW of solar-generated electricity, while the Americas, Africa and Australia are each projected to install approximately 1GW in 2014. This paper takes a look at the development of these emerging markets and provides a projection of likely installation figures up to 2015.
Laser-doped selective emitter (LDSE) technology, invented and patented by the University of New South Wales (UNSW), is presently generating considerable interest in the photovoltaics industry due to its low cost, high efficiency, and suitability for mass production. The excellent results achieved to date – as high as 19.7% on small area laboratory test devices [1], and 19.0% on industrial large-area 156mm wafers [2] – are attracting a similarly impressive array of commercial partners. Nearly 10 companies are at various stages of implementation of LDSE technology variants into production and pilot production. This paper takes a closer look at the potential for mass production of LDSE-based solar cells.
As recently as a couple of years ago, solar panels based on thin-film manufacturing technology were being promoted as the low-cost alternative to crystalline silicon. Not only was it cheaper, but thin film also had a convincing roadmap which guaranteed this cost advantage for the foreseeable future. That was 2008, when persistently high polysilicon prices seemed inevitable as demand for solar electricity boomed. We now know that assumption to be false, and although we all knew polysilicon prices would fall eventually, no one predicted the speed and magnitude with which they crashed: in the space of several months, prices reached the point where any advantage associated with the lower materials costs of thin-film manufacturing were completely blown away.
This article highlights an alternative method for increasing short-wavelength external quantum efficiency (EQE) and hence overall conversion efficiency of mc-Si PV modules via luminescent down-shifting (LDS), a technique originally proposed by Hovel et al. [1] in 1979. The potential for efficiency enhancement via LDS has been either predicted or measured for a wide range of PV technologies (see [2] for a review). However, in this article, we will highlight how LDS can be incorporated into the existing encapsulation layer, avoiding any modification to well-established solar cell manufacturing processes and thus offering the potential of a production-ready technology.
Conversion efficiencies of thin-film silicon solar cells can be increased by nanotexturing of the cells. This nanotexturing step allows for a larger fraction of the incoming light to scatter and diffract, so that both the total absorption of light in the solar cell and the short circuit current is enhanced. In this study, we investigate the optics of thin-film silicon solar cells by numerically simulating Maxwell’s equations by a finite-difference time-domain algorithm. Starting with periodically textured solar cells, the influence of the texture period and height on the quantum efficiency and short circuit current were investigated. With this understanding of the optimized surface texture for periodically textured solar cells, the possibility of interpreting the optics of randomly textured solar cells will be discussed.
The majority of solar module manufacturers use ethylene-vinyl acetate (EVA) copolymer foils as the encapsulant material for solar cells and thin-film modules. Because EVA needs long processing times for curing, thermoplastic process materials that do not employ chemical cross-linking have been coming more and more into focus in the encapsulation sector. This paper takes a look at the mechanical temperature-dependent properties of a variety of such materials.
