Effects of Doping and Electrode Contacts on Performance of Organic Light-Emitting Transistors Based on Pentacene and Tris(8-hydroxyquinoline)aluminum

Heterojunction-based organic light-emitting field-effect transistors (OLEFETs) with a top-contact, long channel geometry were fabricated and comparatively characterized. The neutral cluster beam deposition (NCBD) method was used to successively deposit two layers of p-type pentacene and n-type tris(8-hydroxyquinoline)aluminum (Alq(3)). For doped OLEFETs, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) was used as a highly fluorescent dye dopant to enhance the light-emission efficiency and change the emission color. OLEFETs revealed fine device characteristics based on deposition of highly crystalline active layers. The combination of the highly fluorescent DCM doping and asymmetric electrode configuration (Au and Li:Al or LiF/Al) exhibited efficient energy transfer and enhanced electroluminescence (EL) emission. The operating light-emission mechanisms were discussed based on EL photos acquired using a charge-coupled device (CCD) camera.