Self-healing short-circuits in organic light-emitting diodes and solar cells

Self-healing short-circuits in organic light-emitting diodes and solar cells

Oostra, A.J.
Van den Bos, K.H.W.
Michels, J.J.
Blom, P.W.M.

2013-06-16

Organic materials open the way for large-scale applications of Organic Light-Emitting Diodes (OLED) and solar cells (OPV). These materials can be large-scale processed using printing and coating on rigid and flexible substrates. The resulting devices can therefore be fabricated at low cost for various applications. Production yields suffer, however, from particles which, during processing, become entrapped within the organic multi-layer stack. If these particles are large enough the organic anode is not entirely covered with semiconductor, which may cause a shortcircuit since the organic anode, i.e. poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT/PSS), will be in direct contact with the evaporated cathode. A healing procedure may be helpful here: By treating OLED or OPV device precursors with an oxidizer we may be able to reduce the occurrence of short-circuits in the final device. The purpose of such a treatment is to locally cancel the conductivity of the PEDOT:PSS by oxidation of the electronically conjugated back bone. Subsequent evaporation of the cathode will then no longer lead to short circuits. In this contribution we present the effect of the treatment with aqueous oxidizer solution (i.e. NaClO(aq)) on various physical properties of highly conductive PEDOT:PSS layers. Layer thickness and conductivity have shown to significantly decrease upon treatment at rates that show a relation with treatment time and NaClO concentration. Interestingly, differences in the trends are observed. The thickness of the PEDOT:PSS follows an exponential decay towards a residual. The decay rate of this trend is proportional to NaClO concentration. In contrast, the conductivity follows a steady decrease until a relatively sudden breakdown occurs. The mechanisms explaining these trends will be highlighted, together with an outlook towards application of the methodology to full device structures.

healing
pedot:pss
light-emitting diode
oxidant

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Conference proceedings

conference paper

(c) 2013 Oostra, A.J.; Van den Bos, K.H.W.; Michels, J.J.; Blom, P.W.M.