New Doping Process for Organic Photo-Voltaic Cells Could Change the Solar Energy IndustryJanuary 23, 2017 by Robin Mitchell
A new processing technique allows for the doping of organic PV cells at room temperature.
A new processing technique allows for the doping of organic PV cells at room temperature. What will this mean for next generation solar power generation?
A Trend in Solar Energy
With solar cells gradually decreasing in cost and increasing in efficiency it is no wonder why solar power is becoming one of the most dominant forms of renewable electricity. Unlike other common sources of renewable energy, solar energy is essentially guaranteed for half of the day, depending on the season and location of the cells.
Interestingly, solar cells work even during cloudy days and can produce more electricity during partly cloudy days where direct light from the sun hits the panel and clouds in the distance reflect more light.
Solar panels are one of the lead forms of renewable energy
Even though solar cells are getting better at what they do for a cheaper price there is still the issue with portability as they're presently large and generally heavy. There are folding kits that exist so a phone can be charged on the go but they are usually clumsy or take up large amounts of bag space.
A major step in solar evolution will be the development of wearable solar cells which are light and cheap at the same time—which is exactly what researchers at the Georgia Institute of Technology are aiming for.
Organic PV Cells
Organic technology in electronics has increasingly become popular including the rise of OLEDs, flexible displays, transparent displays, and even printed electronics. One application of organic electronics is in solar cells, which use two types of organic molecules (one electron donor and one electron acceptor) to produce electricity from light.
The organic electronics movement and the semiconductor industry share a common challenge: the need for vacuum environments when doping materials (i.e., injecting charges to change whether a material has an excess number of electronics or lack thereof). Such processing steps are very expensive and require carefully controlled environments which make manufacture difficult. This is one of the contributing factors that makes the production of solar cells expensive.
However, a team of researchers from the Georgia Institute of Technology (along with colleagues from other institutions), have developed a processing technique that not only makes doping solar cells easy but cheaper, as well. Instead of needing a vacuum chamber and the use of physical vapor deposition, the organic films which are to be doped are simply submerged in a solution at room temperature for a few minutes.
The solution consists of mixture of polyoxometalate (PMA and PTA) solutions in nitromethane. The result is p-type electrical doping with a doping depth of just 10nm – 20nm which has a high work function (an important trait for solar cell electrical generation). One important advantage of the doping processing is the improved protection of oxidation against the organic PV cell, which is important for both manufacturing and increased product life.
The organic PV cell produced by Georgia Institute of Technology. Image courtesy of UC Santa Barbara
While the organic PV cells are approximately 13% efficient (whereas standard silicon-based solar cells are approximately 20%), the current trend shows that the efficiency will continue to increase in organic-based devices. But organic devices require less power to produce and are easier to recycle, making them preferable from an environmental point of view. Producing a solar cell that uses more power to be manufactured than what it will produce over its lifetime would be pointless (unless the end application is purely for off-grid power with no environmental concerns).
A Step in Simpler Manufacture
It is believed that such processing techniques will create opportunities for countries such as Africa and Latin America where there is a significant lack of capital for manufacturing. As electronics become more integrated into modern life, the demand for components and devices will naturally increase. Therefore, the demand for manufacturing firms will increase and simpler techniques could enable countries with smaller capital to compete. This could have significant impact on the economies of developing countries.
“Our goal is to further simplify the fabrication of organic solar cells to the point at which every material required to fabricate them may be included in a single kit that is offered to the public. The solar cell product may be different if you are able to provide people with a solution that would allow them to make their own solar cells. It could one day enable people to power themselves and be independent of the grid.” – Felipe Larrain, Ph.D. Student
Simpler manufacturing techniques are not just limited to organic PV cells. Other breakthroughs that are showing a shift in how everyday electronics are being manufactured include printed electronics (especially with the case of the product packaging). Such techniques are ideal for places with limited resources because entire circuits can be designed and printed in-house instead of needing parts manufactured in a different country.
The invention of the immersion doping at room temperature may seem small compared to some advancements, but the potential impact on how everyday electronics are manufactured could be massive.