Miss Xueyan Hou
Miss Xueyan HouResearch Student
- School of Physics and Astronomy
Queen Mary, University of London
327 Mile End Road, London, E1 4NS
Telephone: 0207 882 6561
Title: Purification and Electronic Characterisation of 18 Isomers of the Acceptor Material Bis-PCBM
Abstract: Bis-PCBM, a well known accepter material in organic photovoltaics (OPV) devices, comes as a mixture of several structural isomers; a mixture of isomers with different electronic structures that yields good performance. OPV device based on single bis-PCBM isomer (removing the morphological disorder thereby increasing current) with excellent electronic structure (increasing the open circuit voltage) may bring the power convert efficiency closer to its theoretical maximum. Thus, purifying the mixture to isolated isomers is very important. Here, we achieved this goal using peak-recycling HPLC machine combined with three different columns. Overall, 18 isomers were purified from the mixture in 2 to 5 stages with purity exceeding 99.5% with respect to other isomers. The further UV-Vis absorption spectroscopy and cyclic voltammetry characterisation indicate that the 18 isomers own different electronic structures and their calculated HOMOs, LUMOs, and HOMO-LUMO gaps vary from (-5.673 to -5.402 eV), (-3.901 to -3.729 eV), and (1.664 to 1.883 eV), respectively. Of particular interest is that the LUMO level of one isomer is 0.2 eV above that of PCBM, and 0.1 eV above that of the isomer mixture, which is very significant because the open circuit voltage of fullerene based OPVs is only about 1 V.
This project is supervised by Dr. John Dennis.