| AVS 56th International Symposium & Exhibition | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM-WeM |
| Session: | Organic & Molecular Electronics |
| Presenter: | L. Qian, University of Florida |
| Authors: | L. Qian, University of Florida Y. Zheng, University of Florida J. Xue, University of Florida P.H. Holloway, University of Florida |
| Correspondent: | Click to Email |
A polymer light emitting device (PLED) with an active layer consisting of CdSe/ZnS or CdS/ZnS core/shell quantum dots (QDs), and an electron transport/passivation layer consisting of 5 nm ZnO nanoparticles has been studied. The complete device consists of a glass substrate with the following layers: glass/ITO/PEDOT-PSS/poly-TPD/QDs/ZnO/Al-top-contact. The PEDOT-PSS, poly-TPD, QD, and ZnO layers were all deposited from solutions using spin casting, while the ITO layer was sputter deposited and the Al contact was deposited by thermal evaporation through a shadow mask. Thus the device is predominantly a solution-processed QD-PLED with simple vacuum processing instead of thermal evaporation of multiple organic small molecule layers. The emitted color was tuned from blue (CdS/ZnS) to green or red (CdSe/ZnS) by adjusting the composition and size of the QDs. Use of the ZnO layer reduced the injection voltage for a brightness of ~200 cd/m2 from ~11 to ~2.6 V (green light), and improved the stability with time. For example, an unencapsulated QD-PLED with a ZnO nanoparticle layer exhibited a stable ~200 cd/m2 brightness for 18 hrs in ambient air, while a comparable device without the ZnO layer degraded from 80 to 6 cd/m2 in 3 hrs under the same conditions. The reasons for these improvements will be discussed.