Single layer Alq3, double layer PBD/Alq3 and quantum well PBD/Alq3/PBD structures have been grown by organic molecular beam deposition. Energy levels and optical property of these samples are determined by cyclic voltammetry, optical absorption and photoluminescence (PL). Cyclic voltammetry and optical absorption results indicate that PBD/Alq3/PBD structures can be classified as type I quantum well. The PL experimental results indicate that PL peak, of single layer Alq3 structures do not shift to higher energy with decreasing layer thickness. However, for double layer PBD/Alq3 and quantum well PBD/Alq3/PBD structures, PL peaks shift to higher energy with decreasing layer thickness. The reason for blue shift of PL in organic quantum well structures is discussed in light of the theoretical and experimental results published in the literature.
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