By courtesy of:
Yong Cao, Ian D. Parker, Gang Yu, Chi Zhang & Alan J. Heeger
Nature 1999, 397, 414
and two papers cited inside:
Measurement of absolute photoluminescence quantum efficiencies in conjugated polymers
N.C. Greenham, I.D.W. Samuel, G.R. Hayes, R.T. Phillips, Y.A.R.R. Kessener, S.C. Moratti, A.B. Holmes, R.H. FriendÂÂ
Chem. Phys. Lett. 241, 89 (1995)
and
Electronic states of vapor deposited electron and hole transport agents and luminescent materials for light-emitting diodes
Schmidt, A., Anderson, M. L. & Armstrong, N. R.
J. Appl. Phys. 78, 5619 (1995)