Researcher make commercially viable 24.5% efficient perovskite solar PV cells
In an effort to make perovskite solar PV cell with conversion efficiency of 24.5%, chemical and biomolecular engineer Aditya Mohite and others at Rice University designed a chemical solvent to apply on a 2D top layer of desired composition and thickness without destroying the 3D bottom layer and also vice versa. This process ensures higher conversion efficiency as well as higher stability.
Researchers claim their work can lead to commercialisation of efficient and stable bilayer perovskite solar photovoltaic cells. These PV cells measure one micron in thickness.
“This is really good for flexible, bifacial cells where light comes in from both sides and also for back-contacted cells,” Aditya Mohite said. “The 2D perovskites absorb blue and visible photons, and the 3D side absorbs near-infrared.”
Though crystal, cubelike-lattice perovskite material good as converting light into flow of electrons, but this material can be stressed by light, humidity and heat. Mohite and team of his colleagues in this project have worked for years to make perovskite solar cells to last longer and efficient.
“This is significant at multiple levels,” Mohite said. “One is that it’s fundamentally challenging to make a solution-processed bilayer when both layers are the same material. The problem is they both dissolve in the same solvents."
Another applied physics researcher Andrew Torma at Rice as put it his share of effort to validate the electronic structure of a 2D/3D perovskite solar cell.
“When you put a 2D layer on top of a 3D layer, the solvent destroys the underlying layer,” Andrew Torma said. “But our new method resolves this.”
Mohite said 2D perovskite cells are stable, but less efficient at converting sunlight. 3D perovskites are more efficient but less stable. Combining them incorporates the best features of both.
“This leads to very high efficiencies because now, for the first time in the field, we are able to create layers with tremendous control,” he said. “It allows us to control the flow of charge and energy for not only solar cells but also optoelectronic devices and LEDs.”
The efficiency of test cells exposed to the lab equivalent of 100% sunlight for more than 2,000 hours “does not degrade by even 1%,” he said. Not counting a glass substrate, the cells were about 1 micron thick.
Solution processing techniques such as spin coating, dip coating, blade coating, slot die coating and others can be used to deposit material on a surface in a liquid. Once the liquid evaporates, coating stays.
A researcher named Siraj Sidhik used strong artificial sunlight to expose a bilayer perovskite cell for 2,000 hours, to find efficiency drop by 1%.
The secret recipe of solvent is its dielectric constant and Gutmann donor number. "The dielectric constant is the ratio of the electric permeability of the material to its free space. That determines how well a solvent can dissolve an ionic compound. The donor number is a measure of the electron-donating capability of the solvent molecules." explained in the release.
“If you find the correlation between them, you’ll find there are about four solvents that allow you to dissolve perovskites and spin-coat them without destroying the 3D layer,” Mohite said.
Another important point to note when it comes to manufacturing of these cells is, they can be produced using a present commercial process using roll-to-roll manufacturing with capability to produce 30 meters of solar cell per minute.
“This breakthrough is leading, for the first time, to perovskite device heterostructures containing more than one active layer,” said co-author Jacky Even, a professor of physics at the National Institute of Science and Technology in Rennes, France. “The dream of engineering complex semiconductor architectures with perovskites is about to come true. Novel applications and the exploration of new physical phenomena will be the next steps.”
“This has implications not just for solar energy but also for green hydrogen, with cells that can produce energy and convert it to hydrogen,” Mohite said. “It could also enable non-grid solar for cars, drones, building-integrated photovoltaics or even agriculture.”
Author: Srinivasa Reddy N