Researchers at North Carolina State University (NCSU) and the Chinese Academy of Sciences (CAS) have discovered a new, simple and low-cost approach to increase solar cell efficiency.
The researchers have found that the new method easily modifies the molecular structure of a polymer commonly used in solar cells that is claimed to increase solar cell efficiency by more than 30%.
The environmentally safe, flexible, lightweight, inexpensive, efficient polymer-based solar cells have two domains: an electron acceptor and an electron donor material.
CAS chemists have developed the polymer PBT-OP from two commercially available monomers and one easily synthesized monomer, while NCSU researchers conducted the X-ray analysis of the polymer's structure and the donor:acceptor morphology.
Excitons must travel quickly to the interface of the donor and acceptor domains to retain the maximum possible amount of the light's energy in order to be harnessed effectively as an energy source.
The researchers claim that PBT-OP can be easily created and a lower HOMO level can be achieved with a simple manipulation of its chemical structure against other commonly used polymers.
During their research, they have recorded an open circuit voltage value of 0.78V for PBT-OP, representing a 36% increase over the approximate 0.6V average from similar polymers.
NCSU physicist Harald Ade said the researchers have found a chemically easy way to alter the electronic structure and enhance device efficiency by capturing a larger fraction of the light's energy, without changing the material's ability to absorb, create and transport energy.
Currently, efficiency is being increased in different ways including adjusting the difference between the highest occupied molecular orbit (HOMO) of the acceptor and lowest unoccupied molecular orbit (LUMO) levels of the polymer, ensuring minimal loss when harvesting excitons, the energy particles created by solar cells when light is absorbed.
Another approach that is a more difficult, multi-step process, but more commonly used, is to increase efficiency is adding a fluorine atom to the polymer's molecular backbone that will also attract significant material fabrication costs.