量子点电致发光器件发光层能级变化与驱动电压的关系研究

Research on the Relationship Between the Level Changes and Driving Voltage in the Light Emitting Layer of QLEDs

摘要:

以量子点电致发光器件(QLED)中能级分布和载流子浓度的关系为理论基础, 研究了QLED发光层能级变化与驱动电压的关系, 建立了数学模型。以CdSe/ZnS核壳结构量子点为发光层, 计算了器件正常发光时的阈值电压, 分析了电流密度与量子点中电子准费米能级与空穴准费米能级之差的关系。结果表明, 当驱动电压大于9.8V时, CdSe/ZnS中电子的准费米能级与空穴的准费米能级之差大于1.03eV, 量子点电致发光器件正常发光; 理论模型证实由于电子在发光层与电子传输层界面的大量积聚, 导致淬灭发生, 降低发光效率。

Abstract:

Based on the the relationship between energy distribution and carrier concentration in quantum dot electroluminescence devices(QLED) , a theoretical model about the level changes and the driving voltage was developed. Using CdSe/ZnS quantum dots core-shell structure as the emitting layer, the threshold voltage of OLEDs at normal luminescence was computed, and the relationship of the current density and the quasi-fermi level difference between the electron and the hole was analyzed. The theoretical results show when the driving voltage is higher than 9.8V, the quasi-fermi level difference is bigger than 1.03eV, then the device illuminates normally. The theoretical model confirms that the cumulatiion of lots of electrons at the interface between the light emitting layer and the electron transport layer leads to quenching and reduces the luminescence efficiency.