Investigation of emission location in top-emitting green organic light-emitting devices by optical analysis

A series of top-emitting organic light-emitting devices with different thicknesses of carrier transporting layers (N,N′-di(1-naphtyl)-N,N′-diphenylbenzidine, tris(8-hyroxyquinloine) aluminum (Alq₃)) and emitting layer (EML, 10-(2-Benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyropyrano(6,7-8-i,j)quinolizin-11-one (C545T)-doped Alq₃) were fabricated. C545T-doped Alq₃ was found to bring about double recombination peaks in EML. As the distance between EML and reflective anode was increased, the outcoupling efficiency greatly deviated from optically-simulated values due to charge imbalance in EML and optical loss at the EML/Alq₃ interface. The device with 30 nm of EML exhibited maximized outcoupling efficiency and further increase of EML thickness brought about decrease in efficiency due to decrease in hole-electron recombination at the EML/Alq₃ interface.     

Extracting evolution of recombination zone position in sandwiched solid-state light-emitting electrochemical cells by employing microcavity effect

Techniques of probing for time-dependent evolution of recombination zone position in sandwiched light-emitting electrochemical cells (LECs) would be highly desired since they can provide direct experimental evidence to confirm altered carrier balance when device parameters are adjusted. However, direct imaging of recombination zones in thin emissive layers of sandwiched LECs could not be obtained easily. In this work, we propose an alternative way to extract evolution of recombination zone position in sandwiched LECs by utilizing microcavity effect. Recombination zone positions can be estimated by fitting the measured electroluminescence spectra to simulated output spectra based on microcavity effect and properly adjusted emissive zone positions. With this tool, effects of modified carrier transport and carrier injection on performance of LECs are studied and significantly altered carrier balance can be measured, revealing that microcavity effect is useful in tracing evolution of recombination zone position in sandwiched LECs.     

垂直耦合悬空型氮化硅微盘光学传感器

提出了一种垂直耦合型悬空氮化硅微盘谐振型传感器,该传感器由一个底部非悬空的接入波导和一个顶部悬空的微盘腔组成,并用实验证明了其具有较高的器件灵敏度和良好的机械稳定性。对于半径40μm的微盘,在1548. 98 nm谐振波长下可以实现超过104的品质因数以及大小适中、5. 66 nm的自由光谱范围。该传感器的灵敏度可通过覆盖不同的有机液体来测量,实验测得值约为554 nm/RIU。该三维传感器的制备与传统的光刻工艺相兼容,利于大批量低成本生产,同时凭借器件尺寸小、工艺简单、检测灵敏度高、响应快、免标记等特点,在国防安全、生物检测和环境监测等方面具有广阔的应用前景。     

Luminescence behavior from amorphous silicon-carbide film-based optical microcavities

All solid-state optical microcavities based on amorphous silicon-carbide films were designed and prepared in conventional plasma chemical vapor deposition system. The resonant cavity mode was clearly observed in the transmission spectrum, which is in well agreement with the pre-designed value. Room temperature photoluminescence spectra were studied which contain both the enhanced emission band at resonant mode and the stop-band edge emission bands. The luminescence intensity is significantly enhanced and the bandwidth is obviously narrowed at the resonant wavelength due to the Si-based optical cavity structures. The modulation effect of cavity on the transmission and emission behaviors was investigated by angle-dependent transmission, photoluminescence spectra together with photoluminescence excitation spectra.     

Optical properties of a silicon-nanocrystal-based-microcavity prepared by evaporation

A silicon-based microcavity constituted by a SiO/SiO₂ multilayer and Si/SiO₂ Bragg mirrors was prepared by the evaporation technique. We give details about the microcavity realization process. The optical properties of the Si nanocrystals, obtained by the thermal dissociation of the SiO layers, were analyzed by continuous-wave and angle-resolved photoluminescence (PL) experiments. The results show a strong anisotropy of the light emitted by the silicon nanocrystals for a cavity constituted by mirrors with only two distributed Bragg reflectors (DBR).