Although a flexible solar cell offers exciting, new ways of powering vehicles, clothing, and other smart technologies, manufacturing the photovoltaic component is a challenge.

Researchers at Aalto University in Finland and Université de Montréal are studying whether the now-experimental technology  will someday be ready for mass production and commercialization.

Jaana Vapaavuori, an assistant professor of the chemistry department of Université de Montréal, spoke with Tech Briefs about the manufacturing methods that could decrease the cost and increase the lifetime of flexible solar cells.

Tech Briefs: Which applications will flexible solar cells be most valuable for?

Professor Jaana Vapaavuori: Flexibility will be a key aspect in many portable uses of photovoltaics, and especially consumer product-, textile- and vehicle-integrated solar cells. One of the current visions of the field is wearable devices that could carry their own autonomous power sources, probably combined to flexible batteries. This can be especially beneficial in off-grid conditions and in conditions of less energy security.

Tech Briefs: Why are flexible solar cells so important to develop?

Prof. Vapaavuori: One of the great aspects of flexible dye solar cells is that they can compete with other solar cell types in indoor low-intensity light conditions, which increases their suitability for wearable personal devices. Another, closely related stream of development is replacing different components of dye solar cells with non-toxic or even industrially compostable materials, thus hopefully making it possible to produce flexible solar cells that are easily disposable.

Professor Jaana Vapaavuori shows a sample of a flexible solar cell. (Image Credit: Université de Montréal)

Tech Briefs: What is preventing their everyday use – or more specifically, their mass production?

Prof. Vapaavuori: The two main obstacles that prevent flexible dye solar cells to enter the big markets are the price of production and lifetime of the devices, which both need to still be tackled. The biggest breakthrough in terms of decreasing the costs is to make all the process steps compatible with high throughput roll-to-roll production. A secondary aspect is to replace the existing materials with something that would be less expensive.

An important question is also how to reduce costs by increasing the device lifetime at the same time, since in an ideal case the devices should produce many times more energy than was used for making them. In our work, we identify the encapsulation of the cells as a major bottleneck. Thus, we need to both find encapsulation methods that are roll-to-roll compatible and that would allow sealing the cells in such a way that there would be as little as possible diffusion of water vapor and other impurities into the cell.

Another important field of study is to find flexible substrate materials, which would have very low water vapor transmission rates, since the currently used polymer substrates are clearly not optimal in that aspect.

Tech Briefs: And what is being done to overcome those obstacles? What kinds of work are you currently doing with flexible solar cells?

Prof. Vapaavuori: One important aspect is fundamental research of what makes or breaks a long life of a flexible dye solar cells and my Finnish collaborators are currently very active in this area, for instance by developing the new accelerated aging tests and methods to evaluate the cell lifetime based on electrolyte color changes that can be measured by a digital camera. My recent work has involved developing new printable porous substrates that can be used as sponges for liquid electrolyte component in these cells, which is a step that simplifies the cell-assembly by wiping out the need of having electrolyte filling holes, and thus eliminates one common pathway for cell leakages.

What do you think? Will flexible solar cells someday power your devices? Share your comments below.