Effect of the electric field during annealing of organic light emitting diodes for improving its on/off ratio

(i) The OLED as fabricated (standard). (ii) An OLED annealed, fast cooling, no reverse bias. (iii) As in (ii) except reverse bias during annealing, but not cooling. (iv) As in (iii) with reverse bias also during cooling. (v) As in (iii), except that cooling is slower. (vi) As in (iv), except that cooling is slower.