Efficient Photon Extraction in Top-Emission Organic Light-Emitting Devices Based on Ampicillin Microstructures.

ABSTRACT

The desire to enhance the efficiency of organic light-emitting devices (OLEDs) has driven to the investigation of advanced materials with fascinating properties. In this work, the efficiency of top-emission OLEDs (TEOLEDs) is enhanced by introducing ampicillin microstructures (Amp-MSs) with dual phases (α-/ß-phase) that induce photoluminescence (PL) and electroluminescence (EL). Moreover, Amp-MSs can adjust the charge balance by Fermi level (EF ) alignment, thereby decreasing the leakage current. The decrease in the wave-guided modes can enhance the light outcoupling through optical scattering. The resulting TEOLED demonstrates a record-high external quantum efficiency (EQE) (maximum 68.7% and average 63.4% at spectroradiometer; maximum 44.8% and average 42.6% at integrating sphere) with a wider color gamut (118%) owing to the redshift of the spectrum by J-aggregation. Deconvolution of the EL intensities is performed to clarify the contribution of Amp-MSs to the device EQE enhancement (optical scattering by Amp-MSs 17.0%, PL by radiative energy transfer 9.1%, and EL by J-aggregated excitons 4.6%). The proposed TEOLED outperforms the existing frameworks in terms of device efficiency.