Low Light Amplification Threshold and Reduced Efficiency Roll-Off in Thick Emissive Layer OLEDs from a Diketopyrrolopyrrole Derivative

External quantum efficiency (EQE) roll-off under high current injection has been one of the major limiting factors toward the development of organic semiconductor laser diodes (OSLDs). While significant progress in this regard has been made on organic semiconductors (OSCs) emitting in the blue-green region of the visible spectrum, OSCs with longer wavelength emission (>600 nm) have fallen behind in both material development and the advancement in device architectures suitable for the realization of OSLDs. Therefore, to make simultaneous incremental advancements, a host-guest system comprising of a high performing poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) polymer and an efficient small molecule laser dye, dithiophenyl diketopyrrolopyrrole (DT-DPP), is used. This combination provides an extremely low amplified spontaneous emission threshold of 4.2 mu J cm(-2) at an emission wavelength of 620 nm. The solution-processed organic light-emitting diodes (OLEDs) fabricated using this system exhibit a high external quantum efficiency (EQE) of 2.6% with low efficiency roll-off and high current injection up to 90 A cm(-2) to yield ultrahigh luminance of over 1.5 million cd m(-2).

Automated summary

The roll-off of external quantum efficiency (EQE) under high current injection hampers the development of organic semiconductor laser diodes (OSLDs). While progress has been made in organic semiconductors (OSCs) emitting in the blue-green region, OSCs emitting at longer wavelengths (>600 nm) lag behind in both material development and device architectures. In this study, a host-guest system comprising a high performing polymer and an efficient small molecule laser dye is used to achieve low threshold and high EQE in organic light-emitting diodes (OLEDs) fabricated via solution processing.