Supplementary data for Nanoparticles of poly(3-hexylthiophene): Toward a solvent-independent performance of electrochromic films [Dataset]

Abstract

S1. UV-vis absorption spectra. S2. Redox charge density & thickness. S3. Stationary transmittance at 520 nm. S4. Transmittance spectra. S5. Switching speed. S6. Stability test. S7. Spin-coated P3HT-CHCl3 film. References.

S1. UV-vis absorption spectra: The UV-vis spectra (Figure S1) of P3HT-THF and CHCl3 solutions show a featureless broad π-π* transition absorption band with its maximum at 445 nm, typical for amorphous P3HT. This band is red-shifted to 510 nm for the nanoparticle polymer P3HT (NP) dispersions. The spectra for these dispersions also show the appearance of peaks at 520 nm, 560 nm, and 620 nm, which indicate the existence of vibronic transitions caused by the internal aggregation of the P3HT chains inside the nanoparticles.[1,2] The acquired aggregate structure with its electronic transitions of the P3HT (NPs) in dispersion is maintained when deposited in the form of films onto substrates.-- S2. Redox charge density & thickness: Figure S2 shows the cyclic voltammograms of the different P3HT film probed for different film thicknesses at a scan rate of 20 mV/s in the potential window from -0.3 to 1.1 V vs. Ag/AgCl reference electrode (RE), calibrated at 0.45 V vs. ferrocene. The surface area exposed to the electrolyte is about 1 cm2.-- S3. Stationary Transmittance: Figure S4 show the stationary transmittance curves of the P3HT film series taken at 520 nm in the oxidized and neutral state as a function of the calculated redox charge densities. Experimental data points are fitted by exponential decay functions. The P3HT film series show similar transmittance curves in the oxidized state (Figure S3A), while those in the neutral state (Figure S3B) exhibit larger deviations. The difference between transmittance values in the oxidized and neutral state then provides the contrast curve as a function of the redox charge density as shown in Figure 2 of the main manuscript.--

S4. Transmittance spectra: Figure S4 shows the transmittance spectra of P3HT-THF film acquired in its neutral and oxidized states, reflecting its magenta and transparent pale blue colors, respectively. The transmittance minimum is obtained at 520 nm for the neutral state and provides the reference value at which maximum contrast, i.e. transmittance differences between the oxidized and neutral state is calculated for the different P3HT film series.-- S5. Switching speed: The switching speed of the P3HT films has been determined following the experimental procedure described in the experimental section of the main manuscript. Here the films are submitted to potential steps of variable pulse lengths of 15, 10, 5, 2, 1, 0.5 and 0.25 s between -0.3 and 1.1 V. A representative case study for a P3HT-THF film is depicted in Figure S5.-- S6. Cycling stability: The cycling stability of the P3HT films has been determined following the experimental procedure described in the experimental section of the main manuscript. Here the films are submitted to a number of potential steps between -0.3 and 1.1 V: 300 cycles of 10 s for each step were applied. A representative case study for a P3HT-THF film is depicted in Figure S6.-- S7. Spin-coated P3HT-CHCl3 film: Spin-coating of non-nanostructured P3HT-CHCl3 dispersions, provides a continuous film coverage of the ITO substrate, as can be seen by SEM (Figure S7A) and the profilometry curve of a representative film with average film thickness of 77 nm (Figure S7B). Therefore, the electrochromic transmittance and contrast behavior at 520 nm (Figure S7C) now shows more consistent results, comparable to those of the spray-coated films of the other P3HT series. This especially refers to the optimum redox charge density and maximum contrast being achieved. Equally, t90 switching speed (Figure S7D), as well as the cycling stability (Figure S7E) in the optimum redox window reveal a behavior close to the ones of the other spray-coated film series. However, the spin-coated P3HT-CHCl3 film is prone to delamination issues (Figure S7F), compromising the mechanical integrity of the film, and thus as well the contact to the underlying substrate. This results in the non-linear enhancement of the t90 switching and the decrease of the cycle stability, beyond the established optimum redox charge densities window, as can be seen in Figure S7D and S7E, respectively. The overall electrochromic performance parameters for the spin-coated P3HT-CHCl3 series are summarized in Table S1.