Presently, chemists working to design more efficient organic solar cells rely heavily on “post-mortem” or post-manufacture analysis of the distribution of the constituent materials of the cells they produce.
In other words, if they want to see how the donor and acceptor molecules within the solar cell mix and interact, they must first create the mixture and produce samples that are examined on the molecular level.
The high-performance solar cells we have now, for example, were created through a labor-intensive, trial-and-error approach of developing over 1,000 material combinations and looking at the optimal processing conditions for each one.
Researchers from the North Carolina State University and the Hong Kong University of Science and Technology have discovered a new quantitative relation that allows for quick identification of promising material combinations for organic solar cells.
The discovery could significantly reduce the “trial and error” aspect of solar cell production by reducing the time spent on finding the most efficient mixtures.
Researchers from the Hong Kong University of Science and Technology, set out to determine at what temperature these systems transform from two separate materials to one homogenous mixture in organic solar cells. Utilizing secondary ion mass spectrometry and X-ray microscopy, the team was able to look at molecular interactions at different temperatures to see when the phase change occurs. X-ray scattering allowed them to examine the purity of the domains. The end result was a parameter and quantitative model that describes domain mixing as a function of temperature and that can be used to evaluate different mixtures.
Currently chemists modify a molecule and use trials to see if it is a good material for solar cells, but if they have the wrong processing conditions they could miss a lot of good materials.
However this research measures the saturation level so chemists could determine whether the material system is good before they manufacture devices. The ultimate goal is to form a framework and experimental basis on which chemical structural variation might be evaluated by simulations on the computer before laborious synthesis is attempted.