Extraction of Light Trapped in Special Structured Luminescent Thin Films

Extraction of light trapped in special structured luminescent thin films[pic 1]

               Group discussion                               3rd May 2014

Group members: Barbara Brudieu, Lucie Devys, Prof. Thierry Gacoin, and Gu Rong

1. INTRODUCTION

After almost two months’ internship, with a great help of Barbara and Lucie, I eventually manage to synthesize the DBR and all the solutions needed. Although some techniques still remain to be ameliorated and their theoretical meanings are also left to figure out, to have a small brainstorming at this moment is quite timely I suppose. It just happens to be the mid-point of combining Barbara’s DBR mirror with Lucie’s photonic crystal coupling system. By now, we’ve got three different DBRs (375nm, 620nm, 850nm and the gradient will be fabricated after this meeting) and each mirror has two types: 6 & 8 layers. Several optical measurements (Carry 50) and curves of calibration (TiO2-Eu(TTA)3 layer thickness) will be showed as flowing which are open for discussion. Hope this meeting will assess the work finished so far and give a clear direction for the further steps.

1. DBRs

The optical measurement of these mirrors is operated on Carry 50 and the corresponding simulation is carried out on Matlab (Reticolo).

a.[pic 2][pic 3]

b.[pic 4][pic 5]

c.[pic 6][pic 7]

Figures a, b, c are DBRs of wavelengths 375nm, 620nm and 850nm. Curves left are optical measurement of transmission by Carry 50, curves right are the simulation associated.

The discrepancies between the optical measurement and simulation by Matlab is mainly because for the Matlab simulation, it assumes that for a wavelength inferior to 420nm, all the wave will be absorbed by the glass which is not true compared to the optical measurement. Meanwhile a slightly deviation between the same type of mirror ( e.g, DBR 6C 375-1 & DBR 6C 375-2) in the optical measurement is possibly due to the fact that the condition of subtract surface, spin-coating and annealing process cannot be identical. Also the solution prepared on different days will contribute to the deviation ( e.g, 140425 DBR 6C 620-0 & 140520 DBR 6C 620-1). Though given all facts above, these DBRs can still be considered of relatively good quality.

1. CALIBRATION CURVE OF TiO2-Eu(TTA)3 LAYER

Since the next step concerning depositing a luminescent layer, it’s vital to make sure that the same amount of emitters is present in the different system despite with or without DBRs. If not, the further comparisons won’t make any sense. For this reason, we will first have a discussion of the calibration curve.

[pic 8]

The Cmax or 100% concentration corresponds to a solution of TiO2 40.3 g/L and Eu(TTA)3 20 mg/L. We dilute the mother solution with Ethanol absolute and get different concentrations of solution: 1, 7/8, 3/4, 2/3, 1/2 (fraction of Cmax). After that, we deposit these solutions over a bared glass supplied by Saint-Gobain. The curve above is traced after passing the thickness measurement by two approachs: Profilometre and SEM.