Student: Tanvir Muntasir
Advisor: Vikram Dalal
Title: Understanding Defects in Bulk-heterojunction Organic Solar Cells: Identification, characterization and mitigation
Abstract: Among several thin-film based solar technologies, organic or hybrid organic-inorganic PV technology is envisioned as a foremost candidate toward the realization of ubiquitous and economical solar power. Organic PV (OPV) technology has the advantages of facile fabrication suitable for roll-to-roll processing on flexible substrates, high optical absorption coefficients, low-temperature processing and easy tunability by chemical doping. Substantial progress has resulted from the optimization of materials processing parameters and the emergence of new materials. Recent works have achieved conversion efficiencies exceeding 13%, but with the Shockley-Queisser limit calculated at 21% for single-junction cells, there are many facets left for improvement. Recombination and mobility deficits are considered two of the largest bottlenecks in these devices, accounting for 50-60% of losses. Defect bands can significantly affect both these bottlenecks, introducing charged trap sites, Shockley-Read-Hall centers or both. Thus, the identification, characterization and mitigation of these defects largely remain open and important areas of interest. This talk will focus on understanding defects in OPVs through systematic identification of defects, characterization of their nature and exploring approaches for defect mitigation.