- Post Doctoral
MIT Unit Affiliation:
- Electrical Engineering & Computer Science
Post Doc Sponsor / Advisor:
Date PhD Completed:
Top 3 Areas of Expertise:
Expected End Date of Post Doctoral Position:
My current project is to fabricate and characterize nanostructured photovoltaic devices consisting of molecular and polymeric thin films and colloidal quantum dots.
Polymer based photovoltaic cells are an attractive alternative to conventional inorganic devices due to their potential for less energy intensive processing and easier up-scaling of manufacture via solution processing on flexible substrates. However, their peak efficiency is still too low to make them commercially attractive. The aim of this thesis is to investigate the internal processes that limit solar cell efficiency. In this work we analyzed charge carrier processes in a number of promising polymer solar cells such as bulk heterojunctions of thiophene and phenylene vinylene systems, such as PSHS, PCPDTBT and MDMO-PPV all blended with fullerene systems such as PC61BM or PC71BM. Several techniques were used to assess charge carrier losses in solar cells, such as transient photovoltage/photocurrent, charge extraction and corrected photocurrent. These techniques were also complemented with a numerical model in order to elucidate the results. The techniques employed permit device operation to be probed under realistic working conditions (~ 1sun). Charge carrier losses were found to be dominated by bimolecular recombination and possible other loss processes depending on the material under study. We also found that the voltage at open circuit (Voc) is controlled both by energy level positions and charge loss processes. The results contained herein illustrate how future improvements in device efficiency may be achieved and explain why certain solar cells materials have not performed as expected.