Polarized red, green, and blue light emitting diodes fabricated with identical device configuration using rubbed PEDOT:PSS as alignment layer**Project supported by the National Natural Science Foundation of China (Grant Nos. 61874058, 51861145301, and 61376023), the National Key Basic Research Program of China (Grant No. 2015CB932203), China Postdoctoral Science Foundation (Grant No. 2018M642283), the Synergetic Innovation Center for Organic Electronics and

Abstract

Polarized red, green, and blue light emitting diodes (LEDs) are successfully fabricated using polyfluorene and its derivatives, namely, poly (9,9-dioctylfluorene) (PFO), poly (9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), and poly (triphenylamine-co-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole-co-benzo[c]thiadiazole-co-9,9-dioctyl-9H-fluorene) (Red F). Rubbed hole transport layer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) is employed in the devices as the alignment layer to achieve fully monodomain alignment in all polymer layers. Red F is blended with F8BT to realize the polarized electroluminescence of red light (dichroic ratio ∼3.3), despite having no liquid crystallinity itself. Comparing PFO/F8BT blend to F8BT, higher efficiency of polarized emission is found due to the energy transfer. All the polarized LEDs exhibit pronounced dichroism and efficient polarized emission compared to the non-alignment regular devices.