Most of solar products on the market cannot absorb infrared light with a long wavelength, and there is much room for improvement in conversion efficiency. American scientists discovered a new perovskite material. Solar cells may be able to capture infrared light that accounts for 47% of the spectrum in the future, further enhancing the conversion efficiency.
Sunlight consists of many electromagnetic waves with different wavelengths. UV light accounts for 8%, and visible light and infrared light account for 48% and 44% respectively. The energy of light depends on the length of wavelength. The longer the wavelength, the lower the energy. Short wavelength contains higher energy.
However, the current solar panels cannot effectively capture all the light. When sunlight shines on silicon crystal solar panels, only low energy equivalent to near-infrared light is converted into electricity, and the rest into heat. Silicon crystal solar panels can only absorb near-infrared light, visible light, and UV light, while infrared light with long wavelength cannot be absorbed.
In order to improve the conversion efficiency of solar energy, Florida State University set about studying photon upconversion technology.
The so-called photon upconversion is the process of absorbing two or more photons with longer wavelengths to excite light with shorter wavelength, just like converting infrared light to visible light. Generally, this type of research chiefly adopts metal organic molecules or semiconductor nano-materials. Lawrence Berkeley National Laboratory used organic dye coating to absorb infrared light and convert the light into visible light through the re-emission property.
Lea Nienhaus, a biochemist of Florida State University, said that the team hopes to convert infrared light into light that can be absorbed by solar panels. Different from previous research, however, they used lead-containing halogen perovskite this time, and added the hydrocarbon rubrene to the perovskite to fulfill upconversion for luminescence.
To improve the conversion efficiency and find the ideal perovskite film, the team also tested thin films with different thicknesses of 20, 30, 100, and 380 nanometers. When the thickness exceeds 30 nm, as they discovered, the up-conversion performance can be improved.
However, the team also found that perovskite film will reabsorb visible light generated by upconversion. Researcher Sarah Wieghold also pointed out that the team needs to optimize the proportion of infrared light that is absorbed.
