The analysis of amplified spontaneous emission and luminescence enhancement of BUBD-1 based on host-guest system

The lowest amplified spontaneous emission (ASE) threshold (1.51 μJ/pulse) of CBP: 2 wt%BUBD-1 blend films was about 6 times lower than that of BUBD-1 neat film (9.25 μJ/pulse). The OLEDs with blend film as the emission layer (EML) exhibited an excellent photoelectric performance. In this regard, a series of theoretical analysis were carried out to explain the enhancement of ASE and luminescence performance of BUBD-1 in different aspects. Except for the reducing concentration quenching, a higher Stokes shift, energy transfer efficiency and radiation attenuation rate (kr) happened in the blend films. Moreover, the molecular dipole orientation of EML films at the interface and in thin films were analyzed based on the second-harmonic generation (SHG) method and angle-dependent PL spectra analysis. We find that not only the molecular dipole orientation angle alters in the blend film relative to the neat film, but also the angle is different when the films deposited with different methods. Based on the calculated molecular dipole orientation angle, we propose that the varied dipole angle in the blend film contributed to the device properties too. Our works provide a theory insight into the enhancement of ASE and luminescence properties based on host-guest system.