Investigation of Exciton Recombination Zone in Quantum Dot Light-Emitting Diodes Using a Fluorescent Probe

Xiaoyu Huang; Heng Zhang; Dingxin Xu; Feng Wen; Shuming Chen

doi:10.1021/acsami.7b08574

Investigation of Exciton Recombination Zone in Quantum Dot Light-Emitting Diodes Using a Fluorescent Probe

ACS Appl Mater Interfaces. 2017 Aug 23;9(33):27809-27816. doi: 10.1021/acsami.7b08574. Epub 2017 Aug 14.

Authors

Xiaoyu Huang^{1

2}, Heng Zhang¹, Dingxin Xu¹, Feng Wen², Shuming Chen¹

Affiliations

¹ Department of Electrical and Electronic Engineering, Southern University of Science and Technology , Shenzhen 518055, P. R. China.
² Department of Materials and Chemical Engineering, Key Laboratory of Advanced Material of Tropical Island Resources, Ministry of Education, Hainan University , Haikou 570228, P. R. China.

PMID: 28730806
DOI: 10.1021/acsami.7b08574

Abstract

Exciton recombination zone, where the photons are generated, can greatly affect the performance, such as the efficiency and color purity, of the quantum dot (QD) light-emitting diodes (QLEDs). To probe the exciton recombination zone, 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) is doped into the charge transport layer as a fluorescent sensor; by monitoring the Förster resonant energy transfer (FRET) between QD and DCJTB, the location of the recombination zone can be determined. It is found that the electron transport layer (ETL) has a great impact on the recombination zone. For example, in QLEDs with ZnMgO ETL, the recombination zone is near the interface of the QD/hole transport layer (HTL) and is shifted to the interface of the QD/ETL as the driving voltage is increased, whereas in devices with 1,3,5-tris(2-N-phenylbenzimidazolyl) benzene (TPBi) ETL, the recombination zone is close to the interface of the QD/ETL and moved to the interface of the QD/HTL with the increase in the driving voltage. Our results can also clarify the light emission mechanism in QLEDs. In devices with ZnMgO ETL, the emission is dominated by the direct charge recombination, whereas in devices with TPBi ETL, the emission is contributed by both FRET and direct charge recombination. Our studies suggest that fluorescent probe can be a powerful tool for investigating the exciton recombination zone, light emission mechanism, and other fundamental processes in QLEDs.

Keywords: Förster resonant energy transfer; direct charge recombination; exciton recombination zone; fluorescent probe; light-emitting diodes; quantum dot.