The Device Structure And Performance Of Light-emitting Diodes Of Cu-In-Zn-Se Quantum Dots

Quantum dots(QDs)are excellent fluorescent" materials,which have many advantages such as controllable luminescence spectrum,wide excitation spectrum,narrow emission spectrum,good optical stability and long fluorescence lifetime.Quantum dots are widely used in optoelectronic devices,single electron devices and biomarkers.In this study,we start from the synthesis of Cd-free quantum dots(Cd-free QDs)materials,investigate the electroluminescence of QLEDs based on Cu-In-Zn-Se QDs.Single-light-emitting and white-light-emitting devices are fabricated successfully.(1)By regulating the content of Cu in the component.We find that with the increase of the stoichiometry in the synthesis of Cu,the photoluminescence spectra of the quantum dots are redshift.the emission of quantum dots can be altered.The effects of different cotent of Cu in QDs on the performance of the QLED devices are evaluated with ITO/PEDOT:PSS/TFB/QDs/ZnO/Al structure.With the increase of the proportion of the Cu in QDs,the QLED devices show the increased light intensity and then saturated gradually at higher biases.When the Cu content is 0.15 mmol during the synthesis process,the light brightness of the device is the highest.The peak brightness of the device of 1607 cd/m2 is achieved through the optimization on the thickness of the quantum dot layer from the 10 mg/ml solution of QDs.There is a great improvement over previous known literature.(2)Using the mixture of QDs and TFB instead of single quantum dots as the light-emitting layer to fabricate white light devices,we fabricated the device with ITO/PEDOT:PSS/TFB/QDs:TFB/ZnO/Al white-light devices with color coordinates(0.3494,0.3332)were fabricated by regulating the ratio of TFB and QDs.Furthermore,we fabricated ITO/PEDOT:PSS/TFB/QDs/TFB/ZnO/Al device with structure,and layered structure by inserting a layer of TFB in between the QDs layer and the electronic transport layer ZnO.By adjusting the thickness of this second layer of TFB film,we obtained the optimized white-light emission from the QLEDs.The WQLED of this structure has a brightness of about 600 cd/m2.This is also the first time that this Cu-In-Zn-Se quantum dot has been used as a WQLEDs.