Technical Papers

It is widely acknowledged that, without government subsidies, solar power still cannot compete effectively with conventional sources of electrical energy. As the industry strives to make solar electricity affordable and as a viable alternative to fossil fuels, solar power technology companies are diligently moving towards reducing the manufacturing cost for solar modules. In the case of thin-film solar cells in particular, as a benchmark, the cost of for solar power must be reduced for it to be competitive or to attain grid parity. This paper presents a number of opinions from industry leaders on how best to decrease this vital cost.

The PV industry is expected to eventually reduce its manufacturing costs well below €1/Wp. Major technological changes lie ahead of us for manufacturing wafers, solar cells and modules if this cost target is to be met. In order to focus R&D efforts amongst the myriad options, and to speed up the learning curve, the PV industry (equipment vendors, material suppliers and PV manufacturers) may benefit from collaborative efforts guided by an ITRS-like roadmap. In this paper we present the IMEC roadmap, the target of which is to reduce drastically the amount of pure Si needed per Wp by combining efficiencies beyond 20% with aggressive reductions in wafer thicknesses.

In today’s market, crystalline silicon wafer technology dominates industrial solar cell production. Common devices feature opposing electrodes that are situated at the front and rear surface of the wafer and subsequent front-to-rear interconnection is used for module assembly. This paper reflects the functions which have to be fulfilled for the back-side contact of the solar cell as well as challenges and advances for the two basic classes: full-area and local rear contact formation. While full-area contacting has proven to be a reliable technology for industrial production, local contacting through dielectric layers has yet to be put through its paces in industrial implementation.

To date, the United States’ photovoltaic markets have largely been driven by net-metered residential and commercial customer projects, in large part due to federal, state, and utility incentives (see Fig. 1). The rapid growth of the commercial market in particular can almost entirely be attributed to the development of the well-known ‘solar-services’ business model, also known as the solar performance or the third-party solar model, which began in the early 2000s. In short, the commercial solar market surpassed the residential sector, and in 2008 represented only 10% of the number of installations but well over two-thirds of the annual grid-connected megawatts in the U.S. PV market [1]. This article will provide background information on the U.S. solar markets, and define what a utility solar business model is and the drivers of different model types.

The recent photovoltaic industry shakeout which started around Q3 2008 has faced the overcapacity, credit crunch, and economic crisis that significantly declined the average selling price by 50 - 65%, including the price of thin-film photovoltaic modules. The changing business environment has put significant pressure on all PV manufacturing technologies but more candidly on amorphous silicon thin-film single-junction module manufacturers to advance and scale up the device efficiency and aggressively drive cost reduction. This paper outlines the approach taken at Moser Baer Photovoltaic Technologies India Limited (PVTIL), including process optimization and device management strategies, to enhance the module efficiency (total area) of the single-junction amorphous silicon quarter size, 1.43m2, substrate as manufactured using Applied Materials’ SunFab line.

The main goal of the solar industry is to reach grid parity as soon as possible. This can be achieved by reducing the manufacturing costs, by increasing conversion efficiencies and/or by improving the lifetime of solar modules. Driving down the cost of modules is not straightforward. Commercially available PV modules are typically sold with 20-year warranties, and changing these materials for economic reasons requires extensive material testing and recertification of the new module design. In the following sections, we will focus on the cost drivers of module manufacturing processes and how that could evolve into new module designs.

In today’s PV modules, the solar cells are commonly encapsulated in EVA. During lamination EVA undergoes a crosslinking reaction. From a practical point of view, two major interests arise. For quality control purposes, one needs to know the degree of curing of the EVA encapsulant after lamination. The focus in process optimization is on understanding the kinetics of the crosslinking as a chemical reaction. If this is known (and proven), one can predict appropriate crosslinking conditions (i.e. lamination temperature and time) that have to be matched to reach a certain degree of crosslinking. This contribution mostly deals with this latter aspect. DSC as well as DMA data and model-free kinetics were used in this study to establish the kinetics of the EVA crosslinking process. It was found that both techniques adequately predict the degree of crosslinking for any temperature as a function of the curing time.

Building integrated PV | Despite plenty of hype, BIPV has remained a niche segment in the solar business, held back by a combination of high costs and low efficiencies. But as Ben Willis hears, the high-profile entry of Tesla on to the BIPV scene could herald the start of a new era for the sector. In late October, with all the usual fanfare that accompanies an Elon Musk announcement, the CEO of EV and battery storage manufacturer, Tesla, took to the stage to lift the lid on a heavily trailed new product. Most of Musk’s recent utterances on energy have been about storage, particularly Tesla’s high-profile foray into the world of stationary storage through its Powerwall battery system. But this was something a bit different – a buildingintegrated PV (BIPV) product designed to emulate various kinds of roofing tile and eliminate the need for clunky conventional roof-mounted modules once and for all.

Heat transfer and control of the temperature field are important in the production of silicon solar cell wafers. Present work focuses on the first steps of the production chain, i.e. crystallization and wafering. For the crystallization process, control of heat transfer is crucial for the ingot quality in terms of grain structure, impurity distribution, particle formation, and ingot stresses. Heat transfer is also important during subsequent processes, in particular the wire sawing of the silicon blocks into wafers. The paper emphasises the role of heat transfer and explains the consequences for these processes. Examples from experimental trials and measurements are combined with models and simulation methods.

PV manufacturers can quickly reduce their costs, and increase their yields, by using SEMI standards that were originally designed to help semiconductor fabs deal with power glitches and power costs. SEMI, the global industry association serving the manufacturing supply chains for the microelectronic, display and photovoltaic industries, has two well-established electric power standards that could prove especially useful for PV manufacturing: SEMI F47, which helps equipment deal with power disturbances, and SEMI E3, which helps users understand how much electric power is used in their recipes. This paper provides a method of lowering costs and increasing yield by applying these standards in the PV manufacturing industry.