Fig. 1: Synthesis and characterisation of azo-tz-PEDOT:PSS.
From: Azobenzene-based optoelectronic transistors for neurohybrid building blocks
a Schematics of the proposed organic photoelectrochemical transistor featuring azo-tz-PEDOT:PSS planar gate (with cis photo-isomerization upon UV light irradiation) and spin coated PEDOT:PSS channel. b AFM images of PEDOT:PSS (i) and azo-tz-PEDOT:PSS (ii). c UV-visible spectra with trans-cis isomerization spectra before and after UV light stimulation (violet solid and dashed lines, respectively). d Cyclic voltammograms of PEDOT:PSS (blue solid line) and azo-tz-PEDOT:PSS, before and after 5 min of UV irradiation (violet solid and dashed lines, respectively): a slight reduction of the azo-tz-PEDOT:PSS hysteresis was observed compared to the pristine PEDOT:PSS which can be attributed to the chemical functionalization that involved the use of sodium ascorbate reducing the PEDOT:PSS film with a consequent a reduction in conductivity29. Both polymers showed a capacitive electrochemical behaviour in agreement with literature30. e PEDOT:PSS capacitance before and after 5 min of UV irradiation (blue solid and dashed lines, respectively), azo-tz-PEDOT:PSS capacitance before and after 5 min of UV irradiation (violet solid and dashed lines respectively). f Transfer-characteristics curves of azo-OPECT before and after 5 min of UV irradiation (violet solid and dashed line, respectively) acquired by stepping the gate-source voltage (Vgs) in the range −200–800 mV (50 mV steps), while sweeping Vds in the range −800−100 mV; g Chemical structure of the azo-tz-PEDOT system and energy levels of cis conformer obtained from DFT/TDDFT calculations. Only HOMO −2 /LUMO levels localised on azo-tz (pink box) and HOMO/LUMO + 1 localised on PEDOT (blue box) are displayed. The arrow shows the possible photoinduced electron transfer from the LUMO level (localised on the photoexcited azobenzene) to the HOMO level of the system (localised on the PEDOT backbone).
