A common thiophene-based donor material is poly(3-hexylthiophene), or P3HT. It is soluble in several organic solvents, which makes it compatible with low-cost solution processing. Another donor material is poly(3,3///-didodecyl quaterthiophene), or PQT-12. Their molec­ular structures are shown in Figure 6.34. The optical absorption spectra of these compounds (Figure 6.35) show that their absorption bands are […]

The absorption of sunlight in a molecular organic semiconductor results in the formation of molecular excitons, and in accordance with the dipole process and the discussion in Sections 3.6 and 3.7 the ground-state singlet is excited into an excited singlet molecular exciton. This exciton is localized to a single molecule, which is generally on the […]

Among the highest efficiency dopants are the iridium organometallic complexes. They have a short triplet lifetime of 1-100 ps, which means that radiative recombination is assisted since the normally forbidden radiation from the triplet exciton is somewhat allowed due to spin-orbital interaction in the molecule. This relaxes the requirement that spin is invariant during the […]

The requirements for full-colour display applications of OLEDs include red, green and blue emitters with colour coordinates close to the following values: for green emitters, x = 0.3 and у = 0.6; for red x = 0.62 and у = 0.37; for blue x = 0.14 and у = 0.10. Fluorescent dopants emitting with approximately […]

Suitable host materials must exhibit good electron and/or hole conduction to ensure the recombination of charge carriers and the effective formation of excitons. Their LUMO and HOMO levels must suit the guest molecules: Compared to the guest LUMO level the host LUMO level should lie less deep in energy (closer to the vacuum level). Compared […]

Obviously a key material for successful OLED operation, the LEM must be amenable to a high-quality deposition technique such as vacuum deposition. It also requires the capability to transport both holes and electrons to enable the recombination of these carriers. Moreover, it must effectively allow for the creation of excitons and their decay to generate […]

Materials for the electron transport layer (ETL) have been investigated intensively and several families of candidate materials are known. Intermolecular transport occurs by electron hopping, and a LUMO level that is similar in energy to the workfunction of the cathode and the electron-conducting level in the EIL is required, as shown in Figure 6.14. The […]

The basic requirement of the HTL is good hole conductivity. In conjugated polymers hole conductivity arises through conjugated bonding, and in small-molecule hole transport Liq LiMeq Liph LiOXD Figure 6.17 Organo-metallic complexes may also be used for the electron injection layer. Examples are shown consisting of some lithium-quinolate complexes. Liq, LiMeq, Liph and LiOXD. Chemical […]