Solution-processed double-layered hole transport layers for highly-efficient cadmium-free quantum-dot light-emitting
Optics Express
|April 1, 2020
Summary
We developed novel double hole transport layers (HTLs) using TFB and TPD to enhance heavy-metal-free quantum-dot light-emitting diodes (QD-LEDs). This approach significantly improves device efficiency and charge balance for better performance.
Area of Science:
- Materials Science
- Optoelectronics
- Nanotechnology
Background:
- Heavy-metal-free quantum-dot light-emitting diodes (QD-LEDs) lag behind CdSe-based devices in performance.
- Unbalanced charge injection and transport hinder the efficiency of these eco-friendly QD-LEDs.
Purpose of the Study:
- To improve the performance of heavy-metal-free Cu-In-Zn-S(CIZS)/ZnS-based QD-LEDs.
- To investigate the use of solution-processed double hole transport layers (HTLs) for enhanced charge injection and transport.
Main Methods:
- Fabrication of QD-LEDs utilizing double HTLs composed of poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenyl-amine (TFB) and N,N'-Bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine (TPD).
- Optimization of TFB and TPD layer thicknesses and TPD annealing temperature.
- Characterization of device performance, including external quantum efficiency (ηEQE) and current efficiency.
Main Results:
- Achieved a maximum external quantum efficiency (ηEQE) of 3.87% and a current efficiency of 9.20 cd A-1 with optimized double TFB/TPD HTLs.
- Observed a best ηEQE of 5.61% and a mean ηEQE of 4.44% by optimizing TPD annealing temperature.
- Demonstrated superior performance compared to devices with single-layer or blended HTLs.
Conclusions:
- Solution-processed double HTLs, particularly TFB/TPD, effectively enhance the performance of heavy-metal-free QD-LEDs.
- Optimized HTL structure and annealing conditions lead to reduced hole injection barriers, increased hole mobility, and suppressed charge transfer.
- The findings pave the way for more efficient and stable heavy-metal-free QD-LEDs.
