Experimental and computational devices on the way to quantum-dot based light-emitting electrochemical cells
R.F. Ubbink (TU Delft - Mechanical Engineering)
M. Alimoradi Jazi – Graduation committee member (TU Delft - ChemE/Opto-electronic Materials)
A. J. Houtepen – Graduation committee member (TU Delft - ChemE/Opto-electronic Materials)
J.M.C. Mol – Mentor (TU Delft - (OLD) MSE-6)
P. Taheri – Graduation committee member (TU Delft - (OLD) MSE-6)
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Abstract
Due to their simple structure and the possibility for in situ doping, light emitting electrochemical cells (LECs) are shaping up to be a cheap and easily produced alternative to LEDs. To date, little research has been done to combine the luminescent properties of colloidal quantum dots (QDs) with the LEC concept. In this thesis, steps are taken towards developing a QD-based LEC. The LECs were produced based on the semiconducting polymer MEH-PPV, ZnO and CdSe/CdS/ZnS quantum dots. Furthermore, drift-diffusion simulations were performed to discover general trends in LECs. MEH-PPV devices performed as expected. ZnO QDs were found to be unsuitable for LECs due to their high intrinsic conductivity and low luminescence efficiency, while CdSe/CdS/ZnS QDs were identified as promising candidates. Results from the drift-diffusion simulations suggested that unlike in LEDs, the type of electrode material has little effect on device operation. Charge carrier mobility was identified as the limiting parameter for luminescence intensity. It is thus suggested that improving carrier mobility in QD films is the most important step towards QD-based LECs.