How does the conversion efficiency of solar cells depend on the wavelength of light ?

What is it about?

A solar cell is a device that is used to convert energy from the light into electrical power. They could be used in the future for wireless power transmission. This could potentially be achieved using laser light and other sources. But the conversion efficiency of solar energy to electrical energy is limited. Currently, the highest conversion efficiency of a single junction, single crystal silicon solar cell is 26.1%. There have been many improvements over the years to maximize conversion efficiency. However, there is one principled difficulty to resolve. It is an energy mismatch between sunlight and the energy band gap in solar cells since the sunlight has a wide wavelength range. The authors of this study tested the conversion efficiency of solar cells for different wavelengths of light. They also tested how conversion efficiency varies with the power of the solar radiation.

Featured Image

Photo by Derek Sutton on Unsplash

Photo by Derek Sutton on Unsplash

Why is it important?

Current theory says that if the energy of incident light is less than the band gap, the energy cannot be used by the solar cell. Similarly, if the solar radiation energy exceeds the band gap, the excess energy is lost as heat. This causes a decrease in conversion energy. This study confirmed that a single color light, with energy similar to the band gap, could increase conversion efficiency. Moreover, the study showed that conversion efficiency is almost proportional to the wavelength of light. It is also almost proportional to the logarithm of incident radiant power. The study further confirms that power conversion efficiency for long wavelength, single color light is higher than for white light. KEY TAKEAWAY: This study explains some key factors that add to conversion efficiency in solar cells. Studying these factors can help develop better solar cells. This will help pave the way towards technologies like wireless power transmission.