This course module aims to provide students with an in-depth understanding of the organic optoelectronic devices’ multilayer structure which covers organic light emitting diodes (OLED) and organic photovoltaics (OPV). These devices have opened novel applications in both display applications and solar cells. The characteristic of these devices is their multilayer structure which is crucial for both the outcoupling efficiency for the OLEDs and the external quantum efficiency for the OPVs. The module will cover topics such as the structure of OLEDs and OPVs, the involved organic semiconducting and conducting materials, the methods of simulating their operation based on the electromagnetic theory and the respective modelling for optimization purposes.

The contents of the module are outlined as follows:

1. Multilayer structure of OLEDs

• Transparent conducting materials
• Hole and electron injection organic materials
• Spectral refractive indices for the visible spectrum

2. Calculation models for OLEDs

• Dipole antenna modeling of the excited states
• Ray tracing calculation scheme
• Transmission lines modeling

3. Multilayer structure of OPVs

• Organic photovoltaic materials
• Single and bulk heterojunctions
• Planar and cylindrical geometries
• Spectral refractive index and extinction coefficient
• Perovskite solar cells

4. Calculation models for OPVs

• Transfer matrix modeling
• Transmission lines modeling
• Normal and inclined illumination
• Anisotropy, and interface roughness

Mini project: Short circuit photocurrent calculation for an OPV structure.

Groups of 2-3 students will analyse the structure of an OPV for its external quantum efficiency and thus its respective short circuit photocurrent. The materials of the OPV’s multilayer structure will be followed by the respective spectral refractive indices and extinction coefficients. Through this project, students will have the opportunity to develop a simple software code based on an OPV’s structure modelling method.

Upon successful completion of the course, students are expected to be able to:

• Understand the basic structure of organic semiconducting optoelectronic devices.
• Become familiar with the basic materials that are used in their structure, both for OLEDs and OPVs.
• Understand the problem of the outcoupling efficiency throughout a multilayer structure of an OLED.
• Learn the modeling and the calculation methods of the outcoupling efficiency for OLEDs.
• Understand the problem of the external quantum efficiency for a single and bulk heterojunction multilayer structure for OPVs.
• Learn the methods for the calculation of the short circuit photocurrent for OPVs structure.
• Gain the skills to develop software code using the methods of OPVs’ photocurrent calculation.

A course on Photonics

A course on Optical Communications

A course on Optoelectronics

Student evaluation comes from

• Mini group project x 40%
• Final written exam x 60%

• Stephen R. Forrest, “Organic Electronics: Foundations to Applications”, OXFORD University Press, 1^st edition, 2020
• Mitsuhiro Koden, “OLED Displays and Lighting”, IEEE Press, 1^st edition, 2017
• Barry P. Rand, Henning Richter (editors), “Organic Solar Cells: Fundamentals, Devices, and Upscaling”, CRC Press, 2014

RESEARCH ARTICLES

• A. Neyts, “Simulation of light emission from thin-film microcavities” J. Opt. Soc. Amer. A, vol. 15, p. 962, 1998.
• A. Neyts, “Microcavity effects and the outcoupling of light in displays and lighting applications based on thin emitting films,” Appl. Surface Sci., vol. 244, pp. 517–523, 2005.
• Granlund, L. A. A. Pettersson, and O. Inganas, “Determination of the emission zone in a single-layer polymer light-emitting diode through optical measurements,” J. Appl. Phys., vol. 89, no. 11, pp. 5897–5902, 2001.
• Hartmann, P. Boher, Ch. Defranoux, L. Jolivet, and M.-O. Martin,“UV-VIS and midIR ellipsometer characterization of layers used in OLED devices,” J. Lumin., vol. 110, pp. 407–412, 2004.
• P.Savaidis, N.A.Stathopoulos ‘Simulation of light emission from planar multilayered OLEDs, using a transmission-line model’ IEEE – JQE Vol.45, No 9, pp 1089-1099, 2009.
• A.A.Pettersson, L.S.Roman, and O.Inganas, “Modeling photocurrent action spectra of photovoltaic devices based on organic thin films,” J. Appl. Phys., vol. 86, no. 1, pp. 487–496, 1999.
• C.Roman, W.Mammo, L.A.A.Pettersson, M.R.Andersson, and O.Inganas, “High quantum efficiency polythiophene/C60 photodiodes,” Adv. Mater., vol. 10, no. 10, pp. 774–777, 1998.
• J.Moule, J.B.Bonekamp, and K.Meerholz, “The effect of active layer thickness and composition on the performance of bulk-heterojunction solar cells,” J. Appl. Phys., vol. 100, no. 9, pp. 4503-1–4503-7, 2006.
• M.C.Ng, K.Y.Cheung, M.K.Fung, A.B.Djurisic, and W.K.Chan, “Spectroscopic ellipsometry characterization of polymer-fullerene blend films,” Thin Solid Films, vol. 517, no. 3, pp. 1047–1052, 2008.
• Dennler, K.Forberich, M.C.Scharber, C.J.Brabec, I.Tomiš, K.Hingerl, T.Fromherz, “Angle dependence of external and internal quantum efficiencies in bulk-heterojunction organic solar cells”, J. Appl. Phys., 102, 054516, 2007.
• A.Stathopoulos, L.C.Palilis, S.P.Savaidis, S.R.Yesayan, M.Vasilopoulou, G.Papadimitropoulos, D.Davazoglou and P.Argitis ‘Optical modeling of hybrid polymer solar cells using a transmission line model and comparison with experimental results’ IEEE – JSTQE 16 (6), pp. 1784-1791, 2010.
• A.Stathopoulos, L.C.Palilis, S.R.Yesayan, S.P.Savaidis, M.Vasilopoulou, and P.Argitis, “A transmission line model for the optical simulation of multilayer structures and its application for oblique illumination of an organic solar cell with anisotropic extinction coefficient” J. Appl. Phys. 110, 114506, 2011.

Instructor(s): Nikolaos STATHOPOULOS

MRES.B.02.03 – Multilayer structures in Organic Optoelectronic Devices