LEDs Based on Molecular Semiconductors

By using evaporated thin films rather than single crystals of anthracene and per-ylene, Vincett et al. [98] reported drive voltages as low as 12 V, using solid state device structures in which the film is sublimed onto an oxidised aluminium electrode, followed by a semi-transparent gold electrode. External quantum efficiencies in the range 0.03-0.06% were calculated for sublimed film anthracene devices. 

Since then, significant progress has been achieved, first by researchers at Kodak laboratories [91, 99], then in Japan [100-103], using small molecules, such as Alqj and oxadiazoles, both as charge-transporting layers and as emissive layers, either blended within a polymeric host or deposited as sublimed films. 

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