Nanoparticle Paste to Increase Solar Cell Efficiency
A new way to increase the efficiency of perovskite-based solar cells has recently been developed by a team of international researchers from ITMO’s School of Physics and Engineering and Tor Vergata University of Rome.
Results of the study have since been published in Nano Energy.
According to ITMO’s Department of Physics, the researchers developed a paste made from titanium dioxide (TiO2) and resonant silicon nanoparticles to serve as an additional layer in the process of producing solar cells.
The paste, which consists of Mie-resonant particles, reportedly made it possible to both control the amount of light absorbed and also increased the generation of photocurrent, allowing the team to bring the efficiency of solar cells up 21%.
The experiments were conducted on halide (MAPbI3) perovskites. However, because a MAPbI3 perovskites’ photoactive layer is only roughly 300-600 nanometers, it is incapable of absorbing all incoming light. They also can not be produced any thicker or else the light is dispersed more actively, resulting in a loss of energy.
One of two strategies can be used to boost the efficiency of perovskite-based solar cells: improving the charge collection or increasing light absorption.
While the first strategy requires using more complex perovskite compositions and introducing additional substances (typically rare metals), researchers from ITMO and Tor Vergata University instead increased the concentration of light inside solar cells.
“We can obtain silicon from sand, so there is almost an endless supply of this material. It would’ve been a strange solution to simply introduce silicon into the perovskite structure, but it could be introduced as a nanoparticle,” explained Sergey Makarov, professor at ITMO’s School of Physics and Engineering.
“Such particles serve as nanoantennae—they catch light and it resonates inside them. And the longer light stays in the photoactive layer, the more of it is absorbed by the material.”
Researchers went on to add that the trick to it all is that silicon nanoparticles of specific sizes are Mie-resonant. Because of this, the nanoparticles can amplify various optical phenomena, including light absorption and spontaneous radiation, working as a nanoantennae.
For it to work successfully, researchers conducted several theoretical calculations and built a model that accounted for electrophysical and optical properties of all layers and nanoparticles when subjected to external radiation and voltage.
Additionally, the team worked to identify the best location for the developed paste. In order to create thin films of controllably varying thickness and concentration, the solar cells are created using a spin coating method that involves sequentially applying liquid layers to one another.
“With liquid methods we can easily portion out the amount of dry nanoparticles in a solution. What we had to decide was in which layer we should place the Mie-resonant particles,” says Aleksandra Furasova, first author of the paper and a junior research associate at ITMO’s School of Physics and Engineering.
“If put in the perovskite layer, they would damage its photoactive regions. If they were to be put in the upper transport layer, the light would mostly have been absorbed by the time it reached the nanoparticles through all of the layers below them. That’s why we placed the nanoparticles in the next layer after the perovskite—this way they are closer to the light source and work as antennae more efficiently.”
According to the researchers, the developed paste is simple to apply and can be used ith solar cells of any composition and configuration. At the same time, there are no additional complications to the production process, while the cost of the resulting devices increases by only 0.3%.
“The paste can be easily applied with other methods, not only with spin coating. It’s a raw universal product that can be used in other types of solar cells, as well as in the production of various devices—photodetectors, harvesters and optoelectronics. Such production is also environmentally-friendly, as we don’t use any rare materials. As a result, we have developed quite a technological solution and we believe the product will be universally applicable and sought-after,” concluded Makarov.
The project was supported by a grant from the Russian Science Foundation.