Abstract
Organic light emitting diodes (OLEDs) operating in the near-infrared spectral region are gaining growing relevance for emerging photonic technologies, such as lab-on-chip platforms for medical diagnostics, flexible self-medicated pads for photodynamic therapy, night vision and plastic-based telecommunications. The achievement of efficient near-infrared electroluminescence from solution-processed OLEDs is, however, an open challenge due to the low photoluminescence efficiency of most narrow-energy-gap organic emitters. Diketopyrrolopyrrole-boron complexes are promising candidates to overcome this limitation as they feature extremely high photoluminescence quantum yield in the near-infrared region and high chemical stability. Here, by incorporating suitably functionalized diketopyrrolopyrrole derivatives emitting at ~760 nm in an active matrix of poly(9,9-dioctylfluorene-alt-benzothiadiazole) and without using complex light out-coupling or encapsulation strategies, we obtain all-solution-processed NIR-OLEDs with external quantum efficiency as high as 0.5%. Importantly, our test-bed devices show no efficiency roll-off even for high current densities and high operational stability, retaining over 50% of the initial radiant emittance for over 50 hours of continuous operation at 10 mA/cm2, which emphasizes the great applicative potential of the proposed strategy.
Highlights
To date, the only metal-free organic systems enabling NIR-EL are D-A compounds[27,28,29,30]
That strong HOMO-LUMO charge transfer transitions usually result into low emission efficiency[31]
We demonstrate, for the first time, efficient and ultra-stable NIR-Organic light emitting diodes (OLEDs) based on diketopyrrolopyrrole derivatives
Summary
The only metal-free organic systems enabling NIR-EL are D-A compounds[27,28,29,30]. F8BT:DPPcy blending ratios were initially tested to optimize both the film quality and the optical properties (full details reported in Fig. S5 of the Supporting Information).
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