Enhanced longterm stability of aluminum solid electrolyte capacitor containing thiophene derivatives as a solid electrolyte

The derivatives of thiophene, 3,4-ethylene-1-methyl-2-oxy-5-thio-thiophene (EMOTT) and 3,4-ethylene-1-propyl-2-oxy-5-thio-thiophene (EPOTT), are synthesized and then, 3,4-ethylenedioxythiophene (EDOT), EMOTT, and EPOTT are polymerized with ferric 4-methylbenzenesulfonate (oxidant) to obtain PEDOT-OMBs, PEMOTT-OMBs, and PEPOTT-OMBs, respectively. The surface conductivity of PEDOT-OMBs shows the highest value among the fabricated materials because PEDOT-OMBs shows the better defined crystalline structure and the doping concentration of PEDOT-OMBs is much higher than that of PEMOTT-OMBs and PEPOTT-OMBs. Capacitance and equivalent series resistance (ESR) of PEDOT-OMBs show the slightly enhanced value compared to PEMOTT-OMBs and PEPOTT-OMBs because of high electrical conductivity of PEDOT-OMBs. The PEDOT-OMBs shows the highest decrease rate of capacitance and increase rate of ESR because the extent of separation between the PEDOT-OMBs and the dielectric is much larger than that of PEMOTT-OMBs and PEPOTT-OMBs since it has the lowest density and hardness compared to other polymerized materials.

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► Polymerized materials substituted alkyl groups show high hardness.
► Enhanced mechanical property forbids separation between dielectric and electrolyte.
► Newly synthesized electrolytes exhibit excellent long term stability performance.