Paper highlights need for correctly measuring solar cell efficiency

February 27, 2012 by Lisa Zyga weblog
A new guide outlines the correct procedures for measuring solar cell efficiency. Image credit: Wikimedia Commons CC BY 3.0

( -- As the pace of solar cell research continues to accelerate, the question for every new design is “what’s its efficiency?” Since measuring how efficiently a solar cell converts sunlight into electricity involves several factors, making a correct measurement can be challenging. Henry Snaith, a physicist at the University of Oxford who designs solar cells, estimates that compounding small mistakes in measuring efficiency can result in overestimations of up to five times that of the actual value.

To address this problem, Snaith has written a guide for researchers on correctly measuring solar cell efficiency for different types of . As he explains in the paper published in Energy & Environmental Science, a uniform method for measuring efficiency is essential for enabling valid comparisons.

“There's an ongoing stream of papers in which it's not entirely clear exactly how the measurements have been made,” Snaith said in an article in Chemistry World. “If, for example, someone claims their hybrid solar cell has an efficiency of 4% when it's really more like 1%, that makes it problematic for someone else to write an exciting paper when they've genuinely improved something to 1.5%.”

One of the most common potential sources of error that Snaith identifies involves how to mask the cells, which determines the size of the test area. Other problems can occur due to light source calibration and how the cell is positioned during testing. Snaith outlines standards for all these steps, and explains how small deviations can inadvertently cause errors.

Snaith emphasized that the purpose of the guide is not to find fault, but to address the challenges involved in the rapidly growing field of solar cell technology that is attracting researchers from diverse backgrounds. He hopes that the guide will encourage new ideas and increase the rate of new breakthroughs.

“The research field of photovoltaics is booming due to the recognized imperative to realize long-term solutions to clean and inexpensive power generation,” he writes. “…If these standard protocols are adhered to across the field, then a much better comparison between literature values of can be made and more rapid and well-directed technological advancements will occur.”

Explore further: Sharp develops solar cell with world’s highest conversion efficiency

More information: Henry Snaith. “How should you measure your excitonic solar cells?” Energy Environ. Sci., 2012, Accepted Manuscript. DOI: 10.1039/C2EE03429H

via: Chemistry World

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5 / 5 (2) Feb 27, 2012
The device efficiency should be defined with respect to how much light of the light in the entire incident plane that it converts to energy, as in a real-world setting.

That is to say, if 1000watts per square meter hits the entire device, the efficiency should be determined by what percentage of 1000watts was actually converted to electricity, as would be the case in real-world application. NOT determining it by some absurd standard like quantum scale dots, which have a lot of wasted space between them, and ignoring light incident on wasted space...that terribly inflates the numbers compared to real world applications.

A PV system's efficiency should therefore be the same standard as a parabolic trough vacuum tube boiler, which is to say:

Watts out / Watts in : over the whole collection surface.

System efficiency vs device efficiency are two different things.

system efficiency suffers with regard to space, since you need access for maintenance via roads and ladders, etc...
1 / 5 (1) Feb 27, 2012
That is to say, if 1000watts per square meter hits the entire device, the efficiency should be determined by what percentage of 1000watts was actually converted to electricity

Was here to say that, the rest of the post was unnecessary though.

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