Abstract
Thermal annealing of the emissive layer of an organic light emitting diode (OLED) is a common practice for solution processable emissive layers and reported annealing temperatures varies across a wide range of temperatures. We have investigated the influence of thermal annealing of the emissive layer at different temperatures on the performance of OLEDs. Solution processed polymer Super Yellow emissive layers were annealed at different temperatures and their performances were compared against OLEDs with a non-annealed emissive layer. We found a significant difference in the efficiency of OLEDs with different annealing temperatures. The external quantum efficiency (EQE) reached a maximum of 4.09% with the emissive layer annealed at 50 °C. The EQE dropped by ~35% (to 2.72%) for OLEDs with the emissive layers annealed at 200 °C. The observed performances of OLEDs were found to be closely related to thermal properties of polymer Super Yellow. The results reported here provide an important guideline for processing emissive layers and are significant for OLED and other organic electronics research communities.
Highlights
Organic light emitting diodes (OLEDs) are highly sought after for display technology and solid state lighting
The results show an optimum annealing temperature of 50 °C, which produced OLEDs that reached a maximum external quantum efficiency (EQE) of 4.09%
This is significantly higher than EQE of OLEDs with Super Yellow emissive layer annealed at 200 °C, which had a maximum efficiency of only 2.72%
Summary
Organic light emitting diodes (OLEDs) are highly sought after for display technology and solid state lighting. The luminance for PFO:F8BT blend OLEDs and EQE for MEH-PPV:DFD blend OLEDs decreased upon annealing the blended emissive layer These reports suggest that there is an optimum temperature for processing the emissive layer and identifying this point is of key www.nature.com/scientificreports/. Among solution-processable conjugated polymer emissive layers, copolymer Super Yellow is one of the most widely used emissive layers in organic light emitting devices including OLEDs3,16–19. Research reports in organic light emitting devices using polymer Super Yellow as emissive layer show a wide range of thermal treatment, from non-annealed films to annealing at temperatures up to 200 °C18,21–24. The thermal properties of polymer Super Yellow and the optical and morphological thin film properties were investigated to explain the trend observed in OLED performance with respect to annealing temperature
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