If redox reactions (oxidation and reduction) are performed on an electrochromic display whose pixel electrode is made of PEDOT:PSS, and counter electrode is of graphite, while some electrolyte is sandwiched between them, in different environments such as temperature increasing from 20, 50, and 90 degree C, and while relative humidity is also increasing from 10%, 20%, 30%, and 40%. What should one expect for the current and voltage levels? What will the effect on oxidation states of PEDOT:PSS have?
the best to find an answer is to search for literature describing the cyclic voltametry behaviour of PEDOT:PSS
Temperature will primarily alter the mobility of cations and anions making up the electrolyte, therefore, affecting the electrical resistance of the system. Changes in resistance are translated into a different ohmic drop, modifying the operating potentials of the device.
The spectral properties of PEDOT:PSS should be virtually unchanged in such a potential range, however, conductivity will be affected. At this point, I would like to direct Your attention to a paper, wherein temperature-induced phenomena were followed by conductivity measurements for PEDOT:PSS: https://www.sciencedirect.com/science/article/pii/S1566119908001791?np=y
The effect of humidity on the operating parameters of the device will largely depend on the design of the device. For a non-sealed device, humidity might result in side reactions at the negatively polarised electrode, leading to a possible deterioration of the optical contrast of the device in time.
Thanks Tomasz Jarosz for a wonderful reply.
The displays which I am working with are based on PEDOT:PSS, which serves both as active material and pixel electrode, carbon as counter electrode and an electrolyte layer sandwich between them in vertical architecture. All of these materials are printed and encapsulated by PET film. I want to study the switching behavior in both directions i.e., oxidation (bleached) and reduction (colored) that how current levels are affected by chaning the humidity and temperature.
If the device is encapsulated, humidity might have little effect, but it's certainly worth investigating in relation to reported barrier properties of PET. If the thickness of the PET around the device is known, you could even estimate the actual amount of moisture making its way into the device and affecting its operating parameters.
If you are going to study switching, colour switching times (upon application of an alternating potential wave) should be strongly dependent on the temperature due to its effect on the mobility of ions.
Looking forward to seeing your paper !
Thanks Tomasz for your valuable guiding reply and compliments.
Well I carried out redox current measurements by putting the display inside a climate chamber and varying the humidity from 20%, to 50%, and to 90%. While keeping the humidity at certain level, I changed the temperature from 10, 20, 30, and 40 deg C and measured the redox current. So redox current measurements were performed for 12 combinations of humidity and temperature. I did not think about the PET's barrier properties rather focused on changing current level due to climate change. But definitely I will think about that too. The redox potentials, which were DC around 3V, are supplied with a microcontroller for >2 sec for every switching event. I found shift in current level due to change of temperature and humidity.
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