{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

05_Laurent_chrgtransport - 644 S Le Roy et al Charge...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
S. Le Roy et al.: Charge Transport and Dissipative Processes in Insulating Polymers: Experiments and Model 1070-9878/05/$20.00 © 2005 IEEE 644 Charge Transport and Dissipative Processes in Insulating Polymers: Experiments and Model S. Le Roy, G. Teyssedre and C. Laurent Laboratoire de Génie Electrique de Toulouse CNRS-Toulouse III University, 118, route de Narbonne 31062, Toulouse, France. ABSTRACT Electroluminescence in insulating polymers signs the existence of potentially harmful excited states because the excess energy can be released through degraded pathways, opening the way to chemical degradation. Excitation mechanisms involve impact excitation/ionization by hot carriers or bi-polar charge recombination. In order to discuss the relative contribution of these processes to light emission in polyethylene, we introduce a numerical model of charge transport postulating a recombination- controlled electroluminescence. Model outputs and experimental measurements are compared for three different protocols of dc voltage application considering especially the simulated recombination rate and the measured light emission. A fairly good agreement is found between model and experiment when considering electroluminescence under constant dc stress. The model fails to describe the measurement under time-varying dc stress suggesting that excitation by hot carriers should be taken into account. Index Terms - Charge carrier processes, electroluminescence, modeling, plastics. 1 INTRODUCTION Polymers submitted to thermo/electrical stress suffer from aging that can drastically affect their functional behavior [1]. Understanding the physical/chemical processes at play during ageing and defining transport regimes in which these mechanisms start to be critical is therefore a prime goal to prevent degradation and to develop new formulations or new materials with improved properties. It is thought that a way to define these critical regimes is to investigate under which conditions (in terms of stress parameters) light is generated in the material by electroluminescence (EL). This can happen through impact excitation/ionization involving hot carriers or upon bi-polar charge recombination [2]. This definition excludes light from partial discharges, which would sign an advanced stage in the degradation process [3]. In a first part of the paper, we shortly discuss the relationship between EL emission and chemical degradation (aging). It is shown that EL is a proof of potentially harmful excited states which can dissipate their excess energy by degraded pathways, opening the way to chemical degradation. In a second part, we briefly review the EL phenomenology under dc, taking polyethylene as a case study. In a third part, a numerical model of charge transport postulating a recombination-controlled electro- luminescence is presented and critically evaluated with special Manuscript received on 17 February 2005, in final form 13 May 2005.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern