Light-emitting devices absorption

The final remark of this section concerns the polaronic transition of m-LPPP around 1.9 eV, where we can observe P2 with its vibronic replica P3 at 2.1 eV. In Figure 9-20 we show this polaronic absorption in m-LPPP as detected by photoin-duced absorption (a), chaige-induced absorption in conventional light-emitting devices (b), and chemical redox-reaction (c). Only under pholoexcilation, which creates both neutral and charged species, the triplet signal at 1.3 eV is also observed. 

In this section, the basic features of light absorption and emission (luminescence) processes in conjugated systems are reviewed. The discussion will focus on poly(/>-phenylenevinylene), PPV, compounds, which provide typical examples of the physical phenomena to be highlighted in the context of polymer-based light emitting devices. 

Neyts K. and Nieto A.U., Importance of scattering and absorption for the outcoupling efficiency in organic light-emitting devices, /. Opt, Soc, Am, A 23 (2006) 1201... 

The photophysical properties of these thiol-stabilized particles, such as PL [155] and optically detected magnetic resonance (ODMR) [156], their dispersion in polymer films in order to fabricate light-emitting devices [157-159], their possible use in telecommunication devices [160], further structural properties unraveled by EXAFS (extended X-ray absorption fine structure) [161-165], and their incorporation into photonic crystals [166-168] and silica spheres [169], have been described and in part reviewed in a number of survey reports [144, 145, 170-173]. 

It is believed that the molecules of these metalated complexes are totally planar. This allows a better 7t-conjugation across the main chain. The ligands are strongly fluorescent but may become phosphorescent when the platinum atom is introduced in the backbone. These optical properties are tracked back to Ttn transitions by a two-photon absorption. The potential for the use of such metallopolymers for electrophospho-rescent polymer light-emitting devices has been discussed [75]. 

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