<H1>Supporting Information</H1>
<H2>i. Film Formation</H2>
<P>Poly(3,4-ethylenedioxythiophene) and poly(styrene sulfonic acid) (PEDT:PSSH) aqueous blends
were purchased from Clevios. The blends are CleviosTM P, CleviosTM P Al 4083, and CleviosTM P CH
8000 which were used to deposit the PEDT:PSSH films S1-3, respectively. The films were prepared by
drop-casting the aqueous blend onto a graphite paper, and letting the drop dry naturally. The thickness of
the films is typically ~10 μm as determined by a surface profiler. The morphology of films S1-3 was
examined using atomic force microscope (AFM) and scanning electron microscope (SEM).
<H2>ii. Electrochemical Characterization</H2>
<P>In the two-electrode electrochemical cell, the graphite electrodes coated with PEDT:PSSH films were
merged in HCl electrolyte, and the distance between the two electrodes is ~ 1.0 cm. The active surface
area of the PEDT:PSSH film on each electrode is ~0.5 cm2. The electrochemical measurements were
performed using an AUTOLAB workstation equipped with potentiostat and galvanostat. In cyclic
voltammogram data collection, the potential was swept from - 0.8 to 0.8 V with a typical rate of 0.05 V/s.
For galvanostatic charge/discharge measurements, the charge and discharge time of the cell was recorded
under a constant current. AC impedance measurements were performed in the frequency range of 100
kHz to 1.0 Hz.
<H3>iii. DC Current-Voltage Measurements of Film S1 and P3HT Film</H3>
<P>Regioregular poly(3-hexyl thiophene) (P3HT) was purchased from Sigma-Aldrich, and was used as
received. 90 mg of P3HT was dissolved in 6 ml of 1,2-chlorobenzene, and the solution was drop cast onto
a graphite substrate to form a film of 10-μm-thickness. Ag conductive paint (RS component, UK) was
then pasted onto the film to form the top electrode with an active area of 2.0 mm2. A similar device was
made using PEDT:PSSH film S1. Then the devices were baked around ~100 oC to remove residual
solvent. A YOGOKAWA GS610 source measurement unit was used to collect current-voltage (IV) curves
of the devices under N2 atmosphere. The results are shown in the inset of Fig. 4d in the main text.
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