Transient brightness, current, and voltage characterization of organic light emitting devices

Transient current-transient voltage [i(t)-v(t)], transient brightness-trans ient current [b(t)-i(t)], and transient brightness-transient voltage [b(t)- v(t)] analysis are introduced as novel organic light emitting device (OLED) characterization methods. These analysis methods involve measurement of th e instantaneous voltage [v(t)] across, the instantaneous current [i(t)] thr ough, and the instantaneous brightness [b(t)] from an OLED when it is subje cted to a bipolar, piecewise-linear applied voltage waveform. Employing the se characterization methods, two important OLED device physics conclusions are obtained: (1) Hole accumulation at the electron transport layer (ETL)/h ole transport layer (HTL) interface plays an important role in establishing balanced charge injection of electrons and holes into the OLED. (2) Hole a ccumulation at the ETL/HTL interface is more important in establishing the ac conduction characteristics than charge trapping in the ETL. (C) 2001 Ame rican Vacuum Society.