Demonstration of the bipolar transport properties of NPBAppl. Phys. Lett. 89, 262102 (2006)S.K. So and S.C. TseDepartment of Physics and Centre for Advanced Luminescence Materials, HKBU, Hong Kong, ChinaPS-C21 The seventh International Symposium on Functional π-Electron SystemsHong Kong Baptist UniversityB. Electron only deviceA unipolar electron device was fabricated with configuration of ITO/BCP(20nm)/NPB(200nm)/Ca/Al.Fig.8 The EL spectra of devices (A), in black solid line; (B) in red dashed line. Blue dotted line is the PL of NPB. Devices energy diagram (in eV) were also shown. Fig.2 Configuration of the TOF setup and sample structureExperimental detailsA. Time-of-flight measurementTime-of-flight (TOF) measurement is the simple and clear technique to evaluate the carrier mobilities in the organic semiconductors. S.K. So e-mail: [email protected]& S.C. Tse e-mail: [email protected]Introduction & AimsN,N’-diphenyl-N,N’-bis(1-naphthyl)(1,1’-biphenyl)-4,4’diamine (NPB), an important organic hole transport for organic light-emitting diodes (OLEDs), is found to possess bipolar transport properties through:a)Time-of-flight (TOF) measurement b)Electron only devicec)
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