Photogeneration and Charge Transport in Liquid Crystalline Organic Semiconductors – Sanjoy Paul

Date: Mon. October 26th, 2015, 12:30 pm-1:30 pm
Location: Rockefeller 221

Organic semiconductors (OSCs) are emerging candidates for the applications in electronic and photonic devices due to material’s low cost and ease of processing. Many materials have been studied to understand the charge generation and transport physics, as well as to develop techniques for facile processing into light emitting diodes, thin film transistors, photovoltaics, and host of other devices. A recurring theme in this effort is the role of disorder in determining critical material parameters, such as mobility and photogeneration efficiency. A particularly useful class of materials in this quest is that of liquid crystalline (LC) OSCs. LCOSCs offer many advantages including facile alignment and the opportunity to study the effects of differing intermolecular geometries on transfer integrals, disorder-induced trapping, and charge mobilities. In this talk, I will present part of my doctoral dissertation works at Kent State University. This includes the photogeneration and charge transport studies in smectic and discotic LCOSC using conventional and novel method based time-of-flight photocurrent measurement technique. First, I will discuss how the alignment of

First, I will discuss how the alignment of LCOSC molecules can improve the charge transport characteristics over macroscopic distances. Secondly, I will discuss how the electrode substrate and its modification change the physics of photogeneration and charge transport mechanism. Lastly, I will discuss a development of a new method to study the photogeneration and transport mechanisms in inhomogeneous OSCs called “scanning time of flight microscopy” (STOFm) which simultaneously obtains 2D images of various charge transport coefficients and polarized transmittance (to have the semiconductor structure) at small scale (µm) across a sample. Experimental results obtained using STOFm in various structured semiconductors such as smectic LCSOC, discotic LCOSC, and LCOSC/polymer phase separated structure will be discussed.