Center for Functional Nanomaterials Seminar

Radiation from the Sun may provide a clean and abundant energy source capable of meeting the world’s needs far into the future. However, present technologies for harnessing the Sun’s power are expensive and therefore have only been implemented for niche applications on a very small scale. New nanoscale materials offer the promise of cheaper manufacturing and high device efficiencies; however, much work remains to be done to meet this promise. In this talk I will discuss two main topics. The first is the use of nanoporous templates to improve the photovoltaic performance of blended poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) active layers in organic solar cells. Confining P3HT:PCBM organic solar cell active layers within thin nanoporous aluminum oxide templates nearly doubles the supported short-circuit current density compared to equivalent unconfined volumes of the same blend, and increases the poly(3-hexylthiophene) hole mobility in the blend by almost 500 times. Furthermore, introducing radial electron contacts by conformal coating of the template provides an additional 50% increase in device efficiency. The second topic will be quantitative characterization of semiconductor nanowires using scanning probe methods. A number of theoretical reports have suggested that nanowire arrays utilizing a radial p-n structure may provide a pathway for creating low cost, high performance photovoltaic devices. Scanning probe techniques are well suited to the study of properties in nanoscale materials as they provide high spatial resolution, low sampling volume, and high sensitivity. Two such techniques and their application to semiconductor nanowire characterization will be discussed: electron-beam induced current (EBIC) and scanning photocurrent microscopy (SPCM). Quantitative determination of minority carrier diffusion lengths and carrier concentration profiles will be presented. Broader applicability of such techniques will b