UCLA

Organic solar devices can provide a cheaper alternative to the current silicon-based solar cell devices. The main disadvantage of organic photovoltaic is their low efficiency. Therefore there is a great need to better understand the mechanism of electron transfer in order to improve the efficiency of these devices. The main goal in my dissertation is to find a more accurate measure of electron transfer in these devices. I have been using theoretical methods to study electron transfer in fullerene derivatives, a common component of organic solar devices.

One such method that we have investigated is time-dependent split (TD-Split) to study A to B electron transfer by a TD evaluation of the lowest energy transition from the ground state of the combined (AB)- system.

Another method that we have developed is the time-dependent ZINDO method (TD-ZINDO) to study absorption. ZINDO is a useful theoretical tool for systems of interest due to its capacity to handle large systems within reasonable times. We were able to perform explicit time calculations with a minimal basis set. The results were then compared with higher order DFT and TDDFT results.

We also used a DFT based method to calculate the charge transfer between very large solvated organic dimers like fullerenes from isolated dimer calculations. In this method, a delocalized bias is applied directly to the Fock matrix of the dimer until the extra electron is balanced between the two molecules in the dimers. Then the transfer rate can be calculated using Marcus theory. These theoretical methods differ in accuracy and speed. In my dissertation, I will present these different methods and compare them to each other and to experimental values.