Manipulating Refractive Index in Organic Light. Emitting Diodes

Transcription

1 Supporting Information Manipulating Refractive Index in Organic Light Emitting Diodes Amin Salehi 1, Ying Chen 2, Xiangyu Fu 3, Cheng Peng 3, Franky So* 2. 1 Department of Physics, North Carolina State University, Raleigh, 27695, USA 2 Department of Material Science and Engineering, North Carolina State University, Raleigh, 27695, USA 3 Department of Material Science and Engineering, University of Florida, Gainesville, 32611, USA Corresponding Author s address: fso@ncsu.edu Variable Angle Spectroscopic Ellipsometry (VASE) Measurement and Modelling of OAD films: In order to measure the refarctive index of the solid and the porous Alq3 films a sample was prepared and measured following Szeto et. al. 1 A 1mm silicone wafer with a 300nm thick oxide layer was used as substrate. A solid layer of Alq3 film with a thickness of 200nm was deposited at 0 degrees on top of the 300nm SiO 2 layer to measure the refractive index of solid Alq3 film. Then Alq3 was deposited at 80 degrees on top of the solid Alq3 layer, to measure the refractive index of the porous Alq3 layer. A cross-sectional SEM image of the sample which was used for VASE measurements is shown in figure S1. For VASE modelling a Bruggman Effective Medium Approximation (BEMA) model is used. In the 1

2 Brugmann EMA model the refractive index of the bottom solid layer and void are considered as the two blended mediums in the porous OAD film. WVASE software was used for all of the VASE modellings in this work. Gaussian oscillators were used for all modellings. A Woollam M2000 was used for VASE measurments. Figure S1. Cross-sectional SEM image of the sample used for ellipsometry measurment. Substrate is a 1mm thick Si wafer with 300nm of thermal oxide layer. A 200nm thick solid Alq3 film at 0 degrees is first deposited to measure the refractive index of the solid Alq3 film. Then a 700nm thick Alq3 layer is deposited at 80 degrees on top of the solid Alq3 film to measure the refractive index of the porous Alq3 film. A Bruggeman Effective Medium Approximation (BEMA) model using the refractive index of the solid Alq3 layer and void is used to find the refractive index of the porous film. 2

3 Figure S2. a) Dispersive refractive index and extiction coefficienct of some of isotropic materials used in OLED devices. b) Dispersive ordinary refractive index and extiction coefficienct of some of birefringent materials used in OLED device. c) Dispersive extraordinary refractive index and extinction coefficient of some of birefringent materials used in OLED devices. 3

4 Figure S3. a) Measured electroluminescence intensity of the OAD and Control OLED device as a function of viewing angle. b) Simulated electroluminescence intensity of the OAD and Control OLED device, as a function of viewing angle. Device structure used in similaution for the Control Device is: Glass/ITO (100nm, n=2.1)/ TAPC (50nm, n=1.68)/cbp:irppy2acac 1:0.07 (20nm, n=1.8)/b3pympm (10nm, n=1.8)/alq3 (60nm, n=1.75) /Al (100nm, n real =0.77, n imaginary =5.62) and for the OAD Device is: ITO (100nm, n=2.1)/ TAPC (50nm, n=1.68)/cbp:irppy2acac 1:0.07 (20nm, n=1.8)/b3pympm (10nm, n=1.8)/alq3 (20nm, n=1.75)/alq3 (40nm, n=1.45)/al (100nm, n real =0.77, n imaginary =5.62). 4

5 Figure S4. TE-polarized power dissipation vs. in-plane wavevector as a function of ITO refractive index. In Figure S4, TE-polarized power dissipation is calculated as a function of ITO s refractive index, to demonstrate the effect of ITO s refractive index on TE waveguide mode. The calculation is based on the control OLED device structure. When the refractive index of ITO is reduced to 1.5 and lower, the TEWG merges into substrate and outcouples into the substrate, leading to an increase in air+substrate contribution. Refrences: (1) Szeto, B.; Hrudey, P. C. P.; Gospodyn, J.; Sit, J. C.; Brett, M. J. Obliquely Deposited tris(8-hydroxyquinoline) Aluminium (Alq 3 ) Biaxial Thin Films with Negative in- Plane Birefringence. J. Opt. A Pure Appl. Opt. 2007, 9,