Interfacial electronic states and charge transfer play an important role in many organic devices, but it has been technically challenging to probe surface electronic states under ambient conditions or at buried interfaces. Developments in two-dimensional (2D) IR-visible sum frequency generation (SFG) spectroscopy have made it possible to study the optical and electronic properties of organic molecules located at a buried interface. We present studies of poly[2- methoxy, 5-ethyl (2'-hexyloxy) para-phenylenevinylene] (MEH-PPV) surfaces using 2D SFG. Surface SFG electronic spectra were obtained by scanning the frequencies of both incident visible and IR beams, and used to study the electronic transitions associated with the C-C stretching of benzene rings. Assuming an oligomer model and a Gaussian conjugation-length distribution, the average conjugation lengths were estimated to be 5.8 monomer units at the MEHPPV/ solid interface and 5.1 monomer units at the air/polymer interface.

Date Published: 20 August 2009
PDF: 9 pages
Proc. SPIE 7396, Physical Chemistry of Interfaces and Nanomaterials VIII, 73960Q (20 August 2009); doi: 10.1117/12.825666

Published in SPIE Proceedings Vol. 7396:
Physical Chemistry of Interfaces and Nanomaterials VIII
Oliver L. A. Monti; Oleg V. Prezhdo, Editor(s)