5-7 OCTOBER

ISFR

2011

179

TOLEDO (SPAIN)STUDY OF OLED END OF LIFE TREATMENTS
L. Barruetabeña1, M. Arieta-Araunabeña1 and C. Delgado1
1GAIKER Technology Center, Parque Tecnológico, 202, 48170 Zamudioe-mail:barruetabena@gaiker.esAbstract
Organic Light Emitting Diodes (OLED) are rapidly evolving and enabling the generation of new Intelligent lighting
applications, delivering flexible, thin, lightweight and power-efficient light sources that can transform the illumination
market. In response to this, and within 7th Framework Programme on Research, Technological Development andDemonstration, Fast2light Project is working on developing novel, cost-effective, high-throughput, roll-to-roll, large area
deposition processes for fabricating flexible OLED foils for intelligent lighting applications. Even more, in order toovercome potential environmental impacts already in the technology development and design phase, Fast2light project
has also investigated the relevant sustainability aspects arising through the whole life cycle of these products, including
their end of life. Considering the growing recycling and valorization targets for electric and electronic waste, and theabsence of suitable routes for flexible OLEDs in the actual schemes, the project has carried out specific research indeveloping, adapting and testing technologies for recovering high added value materials. The research has been focusedon mechanical and chemical recycling alternatives, like delamination, glycolysis and pirolysis. The use of LCA for
evaluating also the different end of life options enables a global perspective, avoiding potential shift of burdens among i.e.
different regions, time-frames and impact categories.

Keywords: OLED, LCA, recycling, de-lamination, glycolysis

1. Introduction
Fast2light project is focused on developing optimized
deposition processes for fabricating light-emitting polymerOLED foils for intelligent lighting applications. The researchcovers all the layers that are part of an OLED lighting foil,
starting by the substrate choice, and introducing highthroughput deposition and patterning methods for all of thenecessary materials [1]. Keeping this global vision, theproject also assesses the environmental impacts from a life
cycle perspective, evaluating the production, the use andend of life stages. In fact, recycling and valorization options
for OLED lighting are key aspects, considering the expected
growth of this emerging waste. Calculations based onmarket research [2] estimate 10.000 t of waste flexible
OLED to be generated in 2022.
Life Cycle Assessment (LCA) methodology has been used
to evaluate environmental impacts of OLEDs. LCA enables
quantifying impacts associated with the use of different raw
materials and energy sources, as well as with the emissionof contaminants in each life cycle phase of the product.
This paper presents the results obtained in the evaluation ofdifferent recycling options for OLEDs and theirenvironmental implications, according to LCA methodology.

2. Materials and Methods
The recyclability assessment is based on the evaluation of
OLED samples developed within Fast2light project (Figure1). The characterization of the samples, together withinformation about production process and productarchitecture, has been used to identify the polymeric natureinteriores libro.indd 179of the substrates, their thermal stability, degradation duringuse, Higher Heating Value and metal content.

Figure 1. OLED sample developed in the project
Different recycling possibilities have been evaluated:
2.1.De-lamination and de-coating process
Previous experience with complex multilayer/coated wastes
recommends the use of chemicals for metal mobilization orplastic layer separation. Caustic soda was used for decoating metal covers and de-laminating organics, to recoversubstrate foils. The effect of concentration, temperature andprocess time has been studied.
2.2. Feedstock recycling: Depolimerization
Given that the OLED substrate materials (PET or PEN) arecondensation polymers, chemical depolymerization byglycolysis appears as a feasible option for recovery of thestarting monomers. Glycolysis reactions have been carriedout in a glass stirred tank reactor at constant temperature
and atmospheric pressure, in the presence of catalyst andexcess ethylene glycol (EG) to promote the formation ofbis(hydroxyethyl) terephtalate (BHET) and bis(hydroxyethyl)
naphthalate (BHEN), from PET and PEN respectively.

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6th International Symposium on Feedstock Recycling of Polymeric Materials

Table 1. Summary of de-lamination and de-coating tests
CNaOH (mol/l)
0.1-7.0t (min)2-45T (ºC)
25-80

environmental profile, with low energy and chemicals
consumption, leading to the recovery of a film with highproperties that can substitute high quality polymers.

Table 2. Summary of glycolysis tests
Catalyst
EG:OLEDt (h)T (ºC)(w/w)(mol:mol)
1% ZnAc
9:1
2200
2.3. LCA of end of life processes
The environmental impact evaluation of the proposed OLED
recycling scheme has been carried out using ReCiPe
methodology [3] and starting from pilot tests data adapted
to simulate scaled up processes. In the case of glycolysis,
different operational scenarios have been studied, in order
to assess the benefits from water and solvent recirculation.

3. Results and Discussion
3.1.OLED sample characterization test results
The OLED substrate assessed is based on PET or PEN,
representing 50-70wt% of the total foil, depending on thedesign. The substrate can become an important waste flow
relatively homogenous, interesting for recycling.
The potential thermal degradation of the substrate foils
during use phase is an important issue for recyclability. TheTGA results of samples which have been subjected to aging
tests (at 80ºC for different run times) show no changes intheir thermal degradation curves.
Metal content analyses confirm that tested OLEDs containdifferent metals (Ag, Al, Cu, etc.). Preliminary calculations
suggest a metal content of about 0.07wt%, but this figure
varies with the evolving OLED designs, and the content invaluable metals can go up to 3%. This variability and thelow sample availability have impeded validating thetechnical and economic feasibility of the metal recovery.
3.2.De-lamination and de-coating test results
De-lamination and de-coating of OLEDs (NaOH 0.5M,50ºC) has proven to be a suitable treatment for the recoveryof the main polymer substrate, clean, free of metals andwithout changes in its chemical nature.
3.3.Glycolysis test results
Depolimerization by means of glycolysis has been
demonstrated as a suitable recycling treatment for therecovery of the starting monomer of OLED substrate foil.
PET as main foil leads to BHET, while PEN leads to BHEN.
Further study is necessary to check how changes in OLED
composition can affect glycolysis products.
3.4.Environmental profile
The LCA results of the waste OLED treatments considered,show that glycolysis accounts for the highest overall impact,associated with its high demand of water and ethylene
glycol and the large volume of wastewater generated. For
this reason the glycolysis scenario with water and solvent
recirculation presents lower impacts (some impacts evenhave negative value, meaning that the benefit is higher thanthe environmental load), although they still exceed thosegenerated by delamination. Delamination shows bestinteriores libro.indd 180

Figure 2. De-lamination andde-coating effect over OLED

Figure 3. BHEN obtained
after glycolysis runs

4. Conclusions
The main recovery target can be focused on the polymeric
substrate and metals, due to the large volume (50-70%depending on OLED architecture) and homogeneity in thefirst case, and in the second case due to their value and theneed to prevent their dissipation in the environment.
Both chemical delamination and glycolysis show good
recovery results, being delamination the process withlowest environmental impact.
Glycolysis can also be considered a suitable option
provided water and solvent recirculation.
Both processes are expected to enable metal recovery in asecond step, which is of high importance due to the content
in precious and rare metals.
However, research is still necessary in order to check theconsistency of these results with different flexible OLED
composition and structures (material properties may affectthe processes), the full mechanical properties ofreprocessed materials and the technical and economic
feasibility of recovering valuable metals.

References[1] www.fastlight.org[2] J. Colegrove. OLED Lighting in 2009 and Beyond: The
Bright Future. 2009. DisplaySearch[3] M.J. Goedkoop, R. Heijungs, M. Huijbregts, A. De
Schryver, J. Struijs, R. Van Zelm. ReCiPe 2008, A life cycle
impact assessment method which comprises harmonised
category indicators at the midpoint and the endpoint level.
First edition Report I: Characterisation; 6 January 2009,http://www.lcia-recipe.net

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