Spin-cast thin semiconducting polymer interlayer for improving device efficiency of polymer light-emitting diodes Available to Purchase

We report that adding a thin $(∼10nm)$ semiconducting polymer interlayer between apoly(styrenesulphonate)-doped poly(3,4-ethylenedioxythiophene) (PEDT:PSS) hole transporter and an emissive semiconductor significantly improves the device efficiency of polymer light-emitting diodes (LEDs). With the interlayer, the external quantum efficiency (EQE) increases from 0.7%(⁠$0.4cd∕A$ at $3.7V$⁠) to 1.9% (⁠$1.0cd∕A$ at $3.3V$⁠) at $100cd∕m2$ for red LEDs and from 1.9%(⁠$6.2cd∕A$ at $3.4V$⁠) to 3.0% (⁠$10.1cd∕A$ at $3.0V$⁠) at $1000cd∕m2$ for green LEDs. An EQE of 4.0% is also observed in blue LEDs (35% increase). The interlayer is spin-coated directly on top of the PEDT:PSS layer from a poly(2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)imino)-1,4-phenylene)) (TFB) solution. This interlayer prevents significant quenching of radiative excitons at the PEDT:PSS interface by acting as an efficient exciton blocking layer.