Highly Efficient Top-Emission Organic Light-Emitting Diodes Based on Ampicillin Micro-Structure

The effort to enhance the efficiency of organic light-emitting devices (OLEDs) has led to the improvement of advanced materials with multiple advantages property. Herein, we present the robust contribution of a widely used antibiotic; ampicillin (Amp) in optoelectronics. The optimum fusion of Amp with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) considerably improved the device efficiency of a single-unit green phosphorescent OLED. The addition of 25% Amp in PEDOT:PSS provided a horizontal interfacial dipole. The dipole suppressed the hole injection by lowering the work function of the anode and improved the charge balance. Moreover, the parallel arrangement of molecules facilitated the generation of J-aggregations which contributed additional/extra excitons to the device. Additionally, to decrease the deviation in the efficiency and stability of Amp based OLEDs, we reinforced the microcavity effect through the top-emission OLED (TEOLED) structure and optimized the annealing conditions. Amp microstructures (Amp-MSs) of various sizes and shapes (α-/β-phase) are induced due to the increase of annealing temperature annealing temperature, time, and pH level, which led to different degenerated energy states and improved device stability. Amp-MSs induce photoluminescence (PL) and electroluminescence (EL). Additionally, Amp-MSs can adjust the charge-balance by Fermi-level (E_F) alignment, thereby decreasing the leakage current and Amp-PEDOT:PSS layer prevented In diffusion. Moreover, the Amp-MSs triggered light scattering through diffuse reflectance, as indicated by angle-resolved reflectance and optical simulations. Therefore, the wave-guided modes were significantly reduced. It can enhance the light-outcoupling through optical-scattering. As a result, it is suggested that high efficiency can be obtained by using carrier harvesting and photon harvesting through electroluminescence, photoluminescence and light scattering based on Amp-MSs. The TEOLED demonstrates an extraordinarily high current efficiency (CE) (maximum ~ 281.3 cdA^-1 and average ~ 264.3 cdA^-1) and EQE (maximum ~ 68.7% and average ~ 63.4%) with a wide color gamut (~118%). The color coordinates were compensated owing to the extension of the spectrum by the Amp-MS (red-shifted by J-aggregated excitons). Moreover, the deconvoluted EL spectra systematically revealed each contribution of Amp-MS in the device EQE enhancement. These findings are expected to enable the development of high-performance optoelectronic/bioelectronic devices.