Periodic multilayer structures fabricated by alternate deposition two different organic materials are recognized as offering unique electrical and optical functions promising for high performance and new functionality devices.Considering the application of organic multilayer structures to various optical devices including highly efficient EL diodes and lasers

it seems desirable to explore material systems with the typequantum-well structure which has been one of the basic structure of semiconductor optical devices.Three periods multilayer structure was fabricated

in which tris(8-hydroxyquinoline) Alq and 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1

3

4-oxadiazole were alternate deposited.The structure of the specimen was: PBD/Alq/ PBD/Alq/ PBD/Alq/PBD

in which the thickness of Alq was 3nm and PBD was 5nm

respectively.From the configuration and the energy band diagrams

the structure of the specimen was like inorganic quantum well structure

so conveniently

it was called organic quantum well structure in this paper

where PBD act as barrier potential and Alq as potential well.The photoluminescence (PL) spectrum of PBD are largely overlapped with the absorption spectrum of Alq

suggesting the possibility of resonance energy transfer or Frster transfer from PBD to Alq.The PL spectrum of the quantum well structure shows only peak at 508nm

which is Alq luminescence.And in the photoluminescence excitation (PLE) spectrum detecting Alq

the peak at 330nm is most dominated

which

c

orresponding the absorption of PBD.So

the PL and PLE spectrum of the specimen prove that the period multilayer structure could possess carrier confinement type Ⅰ energy lineup.Compared the PL spectrum of the specimen with that of the single layer of Alq (20nm)

the emission peak is shifted to higher energy by 20nm and the full width at half maximum (FWHM) is narrowed by 25nm.The phenomena were contributed to the confinement effect of the quantum well structure.Being confined energetically in the narrow potential well

the possibility of the carrier possessing the higher energy states is enhanced and the diffusion of Alq exitons is suppressed

which induce the increase of the higher energy component and decrease of the lower energy component of the PL spectrum.So the PL spectrum is blue shifted and narrowed considerably.