Ultrahigh-radiance TTA-based OLED with 13 kA cm−2 current injection

TL;DR

Researchers developed an OLED with high current injection and efficient light emission, advancing the potential for organic electrically pumped lasers.

Contribution

A TTA-based OLED with 13 kA cm−2 current injection and 56 W cm−2 output power is demonstrated for the first time.

Findings

The OLED achieved 1% external quantum efficiency at 1 kA cm−2 current injection.

The device produced a record output power of 56 W cm−2, enabling population inversion.

Integration with a DBR microcavity resulted in narrow-band emission with 5.5 nm linewidth.

Abstract

Organic semiconductors have been widely utilized in displays, solar cells, detectors, and other fields due to their tunable optoelectronic properties and simple fabrication processes. However, fabricating organic electrically pumped lasers remains an unresolved challenge. The low mobility of organic molecules struggles to sustain the current injection required for electrically pumped lasing, and the free carriers and triplets generated under high current density also quench the gain characteristics. In device fabrication, high-conductivity electrodes and resonant cavities are inevitably accompanied by optical losses, which decrease the quality factor of the resonator and further elevate the threshold current density for electrical pumping. Here, we fabricated an organic light-emitting diode (OLED) with triplet-triplet annihilation (TTA) characteristics and excellent electrical performance, capable of injecting a current density of 13 kA cm−2 under 15-ns electrical pulse driving. By leveraging short-pulse driving to mitigate triplet accumulation and utilizing the TTA effect to suppress singlet-triplet annihilation (STA), the device can still remain nearly 1% external quantum efficiency (EQE) with 1 kA cm−2 current injection and achieved a record-high output power of 56 W cm−2, which can sustain population inversion. The OLED was integrated into a high-quality distributed Bragg reflector (DBR) microcavity with ultrathin electrodes, realizing narrow-band light emission with a spectral linewidth of 5.5 nm under 13 kA cm−2 current injection. This work paves the way for future fabrication of organic electrically pumped lasers with gain characteristics.

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