Soman Anjaly, Sajeev Anjali K, Rajeev Kavya, K N Narayanan Unni
Photosciences and Photonics Section, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram, Kerala 695019, India.
Academy of Scientific and Innovative Research, Ghaziabad 201002, India.
ACS Omega. 2020 Jan 13;5(3):1698-1707. doi: 10.1021/acsomega.9b03979. eCollection 2020 Jan 28.
Organic light-emitting diodes (OLEDs), in general, require multilayer devices and microcavity structures for emission tuning, which increases the complexity and cost of production. Hence, it is imperative to develop techniques for spectral tuning, which employ simplified device structures. In this study, we have selected a tris(8-hydroxyquinolinato)aluminum (Alq): 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1,5,11-(1)benzopyropyrano (6,7-8-,)quinolizin-11-one (C545T)-based OLED and investigated the dependence of the OLED emission on various deposition parameters and the electrical bias. The concentration of the dopant in the emissive layer (EML) was varied from 3 to 50%, and the single dopant emitter as a limiting case was also studied along with studies on the varied deposition rates and EML thickness. By varying the deposition parameters, the emission was observed to change from excitonic green to excimeric yellow. With increased doping concentration, reduction in pure exciton emission with an increase in excimer emission was observed, resulting in electroluminescent spectral red shift. Similarly, electroluminescence spectra have shown different levels of broadening, depending on the deposition rate and thickness of the EML. These effects could be reversed with increasing applied electric field. Thus, it is indicated that, by suitably optimizing the deposition parameters of the dopant material, spectral tuning can easily be obtained, which may form the basis of simplified and cost-effective device structures.
一般来说，有机发光二极管（OLED）需要多层器件和微腔结构来进行发光调谐，这增加了生产的复杂性和成本。因此，开发采用简化器件结构的光谱调谐技术势在必行。在本研究中，我们选择了基于三（8 - 羟基喹啉）铝（Alq）：10 - （2 - 苯并噻唑基） - 2,3,6,7 - 四氢 - 1,1,7,7 - 四甲基 - 1,5,11 - （1）苯并吡喃并（6,7 - 8 - ）喹嗪 - 11 - 酮（C545T）的OLED，并研究了OLED发光对各种沉积参数和电偏压的依赖性。发光层（EML）中掺杂剂的浓度在3%至50%之间变化，还研究了作为极限情况的单一掺杂剂发射体以及不同沉积速率和EML厚度的情况。通过改变沉积参数，观察到发射从激子态绿色变为准分子态黄色。随着掺杂浓度的增加，观察到纯激子发射减少，准分子发射增加，导致电致发光光谱红移。同样，电致发光光谱根据EML的沉积速率和厚度显示出不同程度的展宽。这些效应可以随着施加电场的增加而逆转。因此，表明通过适当优化掺杂剂材料的沉积参数，可以轻松实现光谱调谐，这可能构成简化且经济高效的器件结构的基础。
