In a broad new assessment of the status and prospects of solar photovoltaic technology, MIT researchers say that it is “one of the few renewable, low-carbon resources with both the scalability and the technological maturity to meet ever-growing global demand for electricity.”

Use of solar photovoltaics has been growing at a phenomenal rate: Worldwide installed capacity has seen sustained growth averaging 43 percent per year since 2000. To evaluate the prospects for sustaining such growth, the MIT researchers look at possible constraints on materials availability, and propose a system for evaluating the many competing approaches to improved solar-cell performance.

The analysis is presented in the journal Energy & Environmental Science; a broader analysis of solar technology, economics, and policy will be incorporated in a forthcoming assessment of the future of solar energy by the MIT Energy Initiative.

The team comprised MIT professors Vladimir Bulović, Tonio Buonassisi, and Robert Jaffe, and graduate students Joel Jean and Patrick Brown. One useful factor in making meaningful comparisons among new photovoltaic technologies, they conclude, is the complexity of the light-absorbing material.

The report divides the many technologies under development into three broad classes: wafer-based cells, which include traditional crystalline silicon, as well as alternatives such as gallium arsenide; commercial thin-film cells, including cadmium telluride and amorphous silicon; and emerging thin-film technologies, which include perovskites, organic materials, dye-sensitized solar cells, and quantum dots.

With the recent evolution of solar technology, says Jean, the paper’s lead author, it’s important to have a uniform framework for assessment. It may be time, he says, to re-examine the traditional classification of these technologies, generally into three areas: silicon wafer-based cells, thin-film cells, and “exotic” technologies with high theoretical efficiencies.

“We’d like to build on the conventional framework,” says Jean, a doctoral student in MIT’s Department of Electrical Engineering and Computer Science. “We’re seeking a more consistent way to think about the wide range of current photovoltaic technologies and to evaluate them for potential applications. In this study, we chose to evaluate all relevant technologies based on their material complexity.”

Under this scheme, traditional silicon — a single-element crystalline material — is the simplest material. While crystalline silicon is a mature technology with advantages including high efficiency, proven reliability, and no material scarcity constraints, it also has inherent limitations: Silicon is not especially efficient at absorbing light, and solar panels based on silicon cells tend to be rigid and heavy. At the other end of the spectrum are perovskites, organics, and colloidal quantum dots, which are “highly complex materials, but can be much simpler to process,” Jean says.

The authors make clear that their definition of material complexity as a key parameter for comparison does not imply any equivalency with complexity of manufacturing. On the contrary, while silicon is the simplest solar-cell material, silicon wafer and cell production is complex and expensive, requiring extraordinary purity and high temperatures.

By contrast, while some complex nanomaterials involve intricate molecular structures, such materials can be deposited quickly and at low temperatures onto flexible substrates. Nanomaterial-based cells could even be transparent to visible light, which could open up new applications and enable seamless integration into windows and other surfaces. The authors caution, however, that the conversion efficiency and long-term stability of these complex emerging technologies is still relatively low. As they write in the paper: “The road to broad acceptance of these new technologies in conventional solar markets is inevitably long, although the unique qualities of these evolving solar technologies — lightweight, paper-thin, transparent — could open entirely new markets, accelerating their adoption.”

The study does caution that the large-scale deployment of some of today’s thin-film technologies, such as cadmium telluride and copper indium gallium diselenide, may be severely constrained by the amount of rare materials that they require. The study highlights the need for novel thin-film technologies that are based on Earth-abundant materials.

The study identifies three themes for future research and development. The first is increasing the power-conversion efficiency of emerging photovoltaic technologies and commercial modules.

A second research theme is reducing the amount of material needed per cell. Thinner, more flexible films and substrates could reduce cell weight and cost, potentially opening the door to new approaches to photovoltaic module design.

A third important research theme is reducing the complexity and cost of manufacturing. Here the researchers emphasize the importance of eliminating expensive, high-temperature processing, and encouraging the adoption of roll-to-roll coating processes for rapid, large-scale manufacturing of emerging thin-film technologies.

“We’ve looked at a number of key metrics for different applications,” Jean says. “We don’t want to rule out any of the technologies,” he says — but by providing a unified framework for comparison, he says, the researchers hope to make it easier for people to make decisions about the best technologies for a given application.

Martin Green, a professor at the Australian Centre for Advanced Photovoltaics at the University of New South Wales who was not involved in this work, says the MIT team has produced “some interesting new insights and observations.” He says the paper’s main significance “lies in the attempt to take a unifying look at the issues involved in choosing between PV technologies.”

“The issues involved are complex,” Green adds, “and the authors abstain from betting on any particular PV technology.”

Just keep in mind that along with complexity comes an increase in cost. A far more cost effective, much higher performance technology exists today that does not require this complexity.

It's called "double sided solar panels". Their incredibly high 94.3% PTC to STC performance ratio places then in the top 1/4 percent of all solar modules that are currently available on today's market. They also offer a heat resistant -0.28%/degree C temperature coefficient for better performance in warm/hot climates. And a bone chilling minus 60 degree C extreme cold temperature rating. And when it comes to a home's curb appeal, nothing even comes close to the aesthetics of these double sided glass on glass, see through, frameless construction.

The most complex structure in the upper right of the illustration shows a quantum dot. That happens to be a Tetrapod Quantum Dot and only one company can mass produced those in a quantity sufficient to support use in solar cells, Quantum Materials Corp. if you invest you may want to look into this company, the ticker is QTMM.

The success of Photovoltics in US,Germany and in some countries of Europe is quite difficult from countries like India. Most of the Solar cells used in India are of low efficiency to contain the cost. Apart from that there are major projects coming up in Rajasthan which is a desert are with little water sources. On the other hand during summer Loo,sand storm blows. Nobody carried out a study on the effect of these fast travelling sand particles on the smooth solar panels surface. While choosing the big solar energy projects in desert areas,the closure of DESERTEC giant solar project should be kept in mind. May be growing of CAM plants like Agave and Opuntia on the borders and in large gaps of solar panels will help to draw water from atmosphere Dr.A.Jagadeesh Nellore(AP),India

JPods networks will begin deploying this year. These networks provide a 10x reduction in energy per passenger-mile. Deploying a megawatt of solar collection over each mile of rail gathers about 40,000 vehicle-miles of power per mile per day. Solar assures stable energy supplies as oil supply shocks become ever more likely. The 10x efficiency gain is amplified by the 6X Net Energy advantage solar has over fracked oil.

This demand will create a stable demand for many technologies to scale to commercial viability.

Communally sharing larger grids placed in area for maximum solar absorption, hooked up to a central system could generate power to individual and group dwellings.Solar power like wind power can be sent to specific destinations and stored. The conductive materials should be coated with an abrasive adhesive to eliminate possible ruptures. Conductive lines need to be encased with thermal insulated materials

Reprinted with permission of MIT News