# Electropolymerized furan-based π-conjugated polymers for organic electronics

Harmony Rondeluk, Iheb Driouech, Benjamin Cabannes-Boué, Philippe Loubet, Sylvain Chambon, Adèle Gapin, Henri Cramail, Stéphane Grelier, Cyril Brochon, Laurence Vignau, et al.

► To cite this version:

Harmony Rondeluk, Iheb Driouech, Benjamin Cabannes-Boué, Philippe Loubet, Sylvain Chambon, et al. Electropolymerized furan-based π-conjugated polymers for organic electronics. ACS Sustainable Chemistry & Engineering, 2025, 10.1021/acssuschemeng.5c10589. hal-05370664

HAL Id: hal-05370664

https://hal.science/hal-05370664v1

Submitted on 18 Nov 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
Electropolymerized furan-based π-conjugated polymers for organic electronics

Harmony Rondeluk,<sup>a,b</sup> Iheb Driouech,<sup>c</sup> Benjamin Cabannes-Boué,<sup>b</sup> Philippe Loubet,<sup>c</sup> Sylvain Chambon,<sup>a</sup> Adèle Gapin,<sup>b</sup> Henri Cramail,<sup>b</sup> Stéphane Grelier,<sup>b</sup> Cyril Brochon,<sup>b</sup> Laurence Vignau<sup>a*</sup> and Eric Cloutet<sup>b*</sup>

**Keywords:** Electropolymerization, π-conjugated polymers, bio-sourced, sustainable synthesis, hole transport material, organic photovoltaic cells

**ABSTRACT:** The transition toward sustainable organic electronics requires the development of π-conjugated polymers from renewable resources, using green and metal-free synthesis methods.<sup>1,2</sup> In this context, furan readily obtainable from biomass, offers a promising bio-based building block for designing next-generation conjugated materials. In this study, we report the synthesis and characterization of novel furan-based conjugated polymers *via* electropolymerization. Three precursors were synthesized using a rapid and energy-efficient microwave-assisted method, ensuring a green and scalable approach. Two of these precursors were successfully electropolymerized onto ITO conductive substrates, forming homogeneous thin films. The resulting polymers were analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) to investigate their morphology and film quality. Electrochemical and UV-Vis-NIR spectroscopy studies were conducted to determine their energy levels and optical properties. Furthermore, the polymer films were doped electrochemically by applying an oxidation potential, and chemically *via* the incorporation of F4-TCNQ to modulate their electronic properties. One of the electropolymerized polymers was introduced in an organic photovoltaic cell as a hole transport layer. Preliminary results showed that such bio-sourced electropolymerized π-conjugated material can act as a hole transport layer. These findings demonstrate the potential of bio-sourced furan-based polymers as promising candidates for next-generation organic electronic applications, offering a sustainable alternative to traditional π-conjugated materials.

<footnote><sup>a</sup>Univ. Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, F-33400, Talence, France</footnote>

<footnote><sup>b</sup>Univ. Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, F-33600, Pessac, France</footnote>

<footnote><sup>c</sup>Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400, Talence, France</footnote>
INTRODUCTION

Bio-based furan, an analogue of thiophene,³,⁴ is attracting growing interest and demonstrates significant potential in the field of organic electronics. Bendikov et al. synthesized the first unsubstituted furan-based oligomers *via* Stille coupling and observed superior packing, solubility, and fluorescence properties compared to the corresponding oligothiophenes.⁵ Its conjugated π-electron system facilitates crucial electronic processes such as charge transport and light absorption. Furan-based materials often display high hole mobility, a key property for efficient charge transport in devices like organic photovoltaic cells (OPVs).⁶⁻⁸ The structural versatility of furan plays a significant role in its suitability for OPVs. The furan ring can be readily modified with various substituents, allowing fine-tuning of electronic properties. Importantly, furan can be sustainably sourced through biomass extraction, aligning with eco-friendly material sourcing trends.⁹⁻¹² This versatility extends to device integration, where furan compounds serve diverse roles, such as electron or hole charge carriers, enabling the design of complex architectures for applications in organic electronics. Owing to its conjugated structure, high charge mobility, tunable electronic properties, processability, and versatile applications, furan represents a valuable material for future achievements in the field. This present study explores furfural, a pivotal bio-based furan derivative obtained from xylose, a major component of hemicellulosic biomass, which serves as the key building block for the synthesis of the conjugated polymers. As a renewable platform molecule, furfural represents a sustainable alternative to fossil-based monomers. Its moderately electron-withdrawing aldehyde functionality facilitates polymerization reactions, particularly with electron-deficient comonomers such as cyano derivatives, enabling access to a wide array of functional π-conjugated polymers, including analogues of phenylene cyano vinylene (CN-PPV) motifs. Moreover, furfural is amenable to electropolymerization, making it a promising building block for the fabrication of conjugated polymer films intended for use in organic electronic applications.

CN-PPV-based polymers have demonstrated their potentiality in OPVs¹³⁻¹⁶ and OLEDs¹⁷,¹⁸ due to their high electron affinity, efficient charge transport, and tunable optoelectronic properties. Their π-conjugated structure facilitates broad-spectrum light absorption,¹⁹ while their solution processability supports cost-effective device
fabrication. These characteristics make CN-PPV-based polymers suitable for improving
OPV efficiency and affordability, contributing to sustainable energy solutions.

In this study, we explore the synthesis of furan-based precursors associated with
cyano-vinylene, imine or thiazolothiazole using a microwave reactor (Fig. 1). This latter
enhances synthesis by accelerating reaction rates, improving energy efficiency and
providing precise control over reaction conditions.²⁰,²¹ The resulting precursors possess
two external furan moieties which can be further subjected to electropolymerization
to form π-conjugated polymers films. Electropolymerization is a versatile technique for
deposit polymers on conductive substrates such as ITO by applying an electric potential
to a monomer solution in a conventional three-electrode electrochemical cell.²² This
method allows for precise control over polymerization conditions, enabling the
tailoring of molecular architectures and properties.²³⁻²⁷ The adaptability of this method
to various monomers enables the creation of thin films with uniform thickness, high
adhesion, and versatile applications in fields such as sensors, electrochromic devices,
energy storage, and electronics.²⁸⁻³¹

Organic photovoltaic technology increasingly demands charge-transport layers that combine high performance with environmental sustainability. While electropolymerization has been widely explored for the preparation of conjugated polymers in electrochromic and sensing applications, its use in OPVs remains limited, with only a few reports of electropolymerized films employed as hole-transport layers (HTLs).³²⁻³⁴ To date, no studies have combined bio-sourced precursors with electropolymerization to produce π-conjugated polymers specifically designed for OPV applications. In this work, we report for the first time the synthesis of π-conjugated polymers derived from bio-based furan monomers via electropolymerization and their integration as HTLs in OPV devices. This approach provides precise control over film thickness and morphology directly on the electrode, avoids the use of large quantities of toxic chemicals and metal catalysts, and significantly reduces synthetic steps compared to conventional polymerization methods. Furthermore, we present a full life-cycle assessment (LCA) of both the furan precursor and the electropolymerized polymer, a rare example of sustainability evaluation in the OPV field. Taken together, these results demonstrate a significant step forward in the development of high-performance, sustainable charge-transport materials for organic solar cells.
Finally, our study proposes a more sustainable approach for synthesizing novel bio-
based π-conjugated polymers using sequential microwave-assisted reaction and
electropolymerization. Two π-conjugated polymers films have been successfully
synthesized through the electropolymerization of furan-based precursors. Additionally,
the energy levels of the corresponding polymer, P(PBFA) (Poly[(2Z,2'Z)-2,2'-(1,4-
phénylène)bis(3-(furane-2-yl)acrylonitrile)]) and P(BFTTz) (Poly[2,5-di(furan-2-yl)thiazolo[5,4-
d]thiazole]), have been evaluated (Fig. 2). The furan-based CN-PPV-type polymer P(PBFA) was
then investigated for its optical and electrochemical doping properties prior to its integration
into OPV devices, highlighting its potential for future applications in organic electronics.

**Results and discussion**

Three conjugated furan-based precursors have been obtained by microwave-assisted
reactions. Furfural, a bio-sourced compound, was chosen to generate the precursors PBFA,
PBF1 and BFTTz by reacting with 1,4-phenylenediacetonitrile, p-phenylenediamine, and
dithiooxamide, respectively (Fig. 1).
<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Reaction equations for the synthesis of furan-based precursors: **a.** PBFI ((1E,1'E)-N,N'-(1,4-phenylene)bis(1-(furan-2-yl)methanimine)), **b.** BFTTz (2,5-di(furan-2-yl)thiazolo[5,4-d]thiazole) and **c.** PBFA (1,4-phenylene)bis(3-(furan-2-yl)acrylonitrile), obtained *via* microwave-assisted reactions.</figcaption></figure>

The reactions were carried out under microwave irradiation to optimize the reaction conditions.³⁵ A comparative study was conducted on the synthesis of the three precursors using microwave-assisted and traditional thermal methods, specifically using an oil-heated Schlenk flask. We observed that the microwave irradiations can largely improve the reaction conditions, leading to higher yields and shorter reaction times as shown in **Table 1**.
<table><caption>**Table 1.** Comparative analysis of yields achieved through conventional synthesis versus microwave-assisted synthesis.</caption><thead><tr><th>Precursors</th><th>Conditions<sup>a</sup></th><th>Temperature (°C)</th><th>Time (h)</th><th>Yield (%)</th></tr></thead><tbody><tr><td rowspan="2">PBFA</td><td>Conventional</td><td>65</td><td>6</td><td>75</td></tr><tr><td>Microwave</td><td>65</td><td>1</td><td>86</td></tr><tr><td rowspan="2">PBFI</td><td>Conventional</td><td>130</td><td>18</td><td>73</td></tr><tr><td>Microwave</td><td>100</td><td>1</td><td>83</td></tr><tr><td rowspan="2">BFTTz</td><td>Conventional</td><td>130</td><td>40</td><td>73</td></tr><tr><td>Microwave</td><td>100</td><td>1</td><td>80</td></tr></tbody></table>

All three precursors were obtained in high yields (>80%) under microwave-assisted conditions, highlighting the efficiency and sustainability of the synthetic routes. Each compound was purified in a straightforward and solvent-minimal manner by simple filtration and washing, offering a scalable and environmentally benign approach to furan-based π-conjugated monomers. The structures of the synthesized precursors were confirmed by ¹H NMR spectroscopy, with the corresponding spectra available in the ESI (Figure S7–S9). To assess the electropolymerization²⁹,³² of these furan-based monomers, potential ranges were applied based on their oxidation behavior observed by cyclic voltammetry (Figure S12). A range of 0–2 V vs Ag/AgCl was used for PBFI, while a narrower range of 0–1.5 V vs Ag/AgCl was applied for PBFA and BFTTz. The cyclic voltammograms corresponding to the electropolymerization behaviors of the PBFA, BFTTz and PBFI precursors are shown in Fig. 2.a, b and c respectively. Regarding the oxidation curves of the PBFA and BFTTz precursors, the current density increased steadily with both precursors as a function of the scanning cycles. The continuous scanning led to the formation of the corresponding P(PBFA) and P(BFTTz) polymer films on the working electrode surface. At the same time, an increase in the peak current density indicated that the polymers displayed good electrochemical activities. Moreover, visual inspection through electropolymerization confirmed the formation of colored polymer films on the electrode surface, purple for P(PBFA) and red for P(BFTTz). However, for the PBFI precursor, a decrease in current density was observed during the

<footnote><sup>a</sup>See experimental part</footnote>
scanning process, which may be attributed to the insufficient electrochemical stability of the imine function under the applied potential (Fig. 2.c).

<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Cyclic voltammograms of the electropolymerization of: **a.** PBFA, **b.** BFTTz and **c.** PBF1 in 0.1 M LiTFSI/acetonitrile under a potential scan rate of 50 mV.s⁻¹. **d.** Structures and images of furan-based π-conjugated polymers P(PBFA) and P(BFTTz) films on ITO, formed by electropolymerization.</figcaption></figure>

Cyclic voltammetry of the P(PBFA) and P(BFTTz) polymer films was performed in an acetonitrile solution containing 0.1 M LiTFSI to determine the onset of oxidation (E<sub>ox,onset</sub>) and of reduction (E<sub>red,onset</sub>) potentials (Fig. 3).
<figure><img src="image_4.png" /><figcaption>Fig. 3. Cyclic voltammetry of the electropolymerized a. P(PBFA) and b. P(BFTTz) polymers, in 0.1 M LiTFSI/acetonitrile under a potential scan rate of 50 mV.s⁻¹.</figcaption></figure>

These onset potentials allowed the calculation of the HOMO and LUMO energy levels of the polymers, as well as their bandgap, using eq 1⁴¹ where $E_{ref}^{SHE} = +0.21 V$ vs SHE and $E_{abs}^{SHE} = 4.44 \pm 0.02 V$ and eq 2 (Table 2).³⁶

$$E_{\text{HOMO/LUMO}} = E_{\text{ref}}^{\text{SHE}} + E_{\text{abs}}^{\text{SHE}} + E_{\text{onset, ox/ref vs ref}} \quad (1)$$

$$E_g = \text{HOMO} - \text{LUMO} \quad (2)$$

These measurements reveal that the P(PBFA) polymer exhibits a lower bandgap of 1.91 eV compared to the P(BFTTz) polymer ($E_g = 2.17$ eV). In addition to electrochemical analyses, UV-Vis absorption spectroscopy was used to determine the optical properties of the polymers, including their absorption maxima and optical band gaps. Spectra were recorded for both the monomers and the resulting polymers to assess the impact of π-conjugation. A significant bathochromic shift was observed upon polymerization, indicating extended π-conjugation: absorption maxima for P(PBFA) and P(BFTTz) shifted by +158 nm and +109 nm, respectively (Fig. 4).
<figure><img src="image_5.png" /><figcaption>Fig. 4. UV-Vis absorption spectra of a. BFTTz in CHCl₃ solution and P(BFTTz) thin film obtained after 2 electropolymerization cycles, and b. PBFA in CHCl₃ solution and P(PBFA) thin film obtained after 2 electropolymerization cycles.</figcaption></figure>

From the onset of absorption (671 nm for P(PBFA) and 632 nm for P(BFTTz)), the optical band gaps were estimated at 1.85 eV and 1.96 eV using eq 3 (Table 2).

$$E_{g,\text{optique}} = \frac{h\nu}{A_{\text{onset}}} \quad (3)$$

These values are slightly lower than those obtained from cyclic voltammetry (1.91 eV and 2.17 eV), as commonly reported in the literature. This discrepancy arises from the different electronic transitions probed by optical versus electrochemical methods. Indeed, excitonic effects are significant: the optical gap corresponds to the energy required to form bound electron-hole pairs (excitons), which is generally lower than the electrochemical gap, representing the energy needed to generate free charge carriers.³⁷,³⁸ Moreover, solvation and polarization effects can influence the energy levels of molecular orbitals, as optical measurements are often performed in organic solvents while electrochemical measurements involve electrolytes; these effects can reduce the excited-state energy and lower the optical gap relative to the electrochemical gap.³⁹ Finally, molecular structure and intermolecular interactions, such as π-π stacking and polymer planarity, can affect electron delocalization
and exciton formation, with better molecular organization leading to lower exciton binding energies and thus a smaller optical gap.⁴⁰

<table><caption>**Table 2.** Values of HOMO, LUMO, and $E_g$ values calculated from cyclic voltammetry experiments.</caption><thead><tr><th>Polymer</th><th>E<sub>ox,onset</sub><sup>a</sup><br>(V vs Ag/AgCl)</th><th>HOMO<sup>b</sup><br>(eV)</th><th>E<sub>red,onset</sub><sup>a</sup><br>(V vs Ag/AgCl)</th><th>LUMO<sup>b</sup><br>(eV)</th><th>E<sub>g</sub><sup>c</sup><br>(eV)</th><th>E<sub>g opt</sub><sup>d</sup><br>(eV)</th></tr></thead><tbody><tr><td>P(PBFA)</td><td>0.88</td><td>-5.55</td><td>-1.01</td><td>-3.64</td><td>1.91</td><td>1.85</td></tr><tr><td>P(BFTTz)</td><td>1.24</td><td>-5.89</td><td>-0.93</td><td>-3.72</td><td>2.17</td><td>1.96</td></tr></tbody></table>

To characterize the morphology of the P(PBFA) and P(BFTTz) films, SEM and AFM analyses were performed on electropolymerized films obtained with only one single cycle of voltammetry. Under these conditions, the films exhibited thicknesses of approximately 60 nm for P(PBFA) and 65 nm for P(BFTTz).²⁸ AFM analysis provided insights into surface roughness, showing a root-mean-square (RMS) roughness of 19.8 nm and 16.6 nm for P(PBFA) and P(BFTTz) films respectively, obtained after 1 voltammetry cycle, as depicted in Fig. 5.a and c. Additionally, SEM micrographs revealed a cauliflower-like morphology which agrees with previous reports on electropolymerized films (Fig. 5.b and d).⁴²

<footnote>aMeasured by cyclic voltammetry</footnote>

<footnote>bCalculated with the following Equation 1</footnote>

<footnote>cCalculated with the following Equation 2</footnote>

<footnote>dCalculated with the following Equation 3</footnote>
<figure><img src="image_6.png" /><figcaption>b.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>c.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>d.</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>**Fig. 5.** AFM images of electropolymerized **a.** P(PBFA) and **c.** P(BFTTz) film after one voltammetry cycle in 0.1 M LiTFSI/ACN. Scanning electron micrographs of **b.** P(PBFA) and **d.** P(BFTTz) films highlight their characteristic cauliflower-like morphology.</figcaption></figure>

In subsequent stages of this work, the focus was directed toward the electropolymerized P(PBFA), as it appeared to be the most promising candidate due to its ease of electropolymerization and its ability to undergo both electrochemical and chemical doping, which will be discussed in the following sections. To investigate the doping and dedoping processes of the P(PBFA) film, we employed a combination of electrochemical and UV-Visible-NIR spectroscopy, a technique known as spectroelectrochemistry.43 **Fig. 6** illustrates the evolution of the absorbance spectra of P(PBFA) during electrochemical oxidation as the potential varies from -0.2 V to +1.2 V vs Ag/AgCl. We observed that the absorbance band between 300 nm and 650 nm steadily decreased, while a new band appeared between 650 nm and 1400 nm, which is a clear signature of the doping process through the formation of polarons.44 The extension of this band up to 1400 nm is attributed to highly delocalized charge carriers and strong interchain interactions within the polymer film. Similar NIR features have been reported for other conjugated donor-acceptor polymers upon electrochemical doping.45
<figure><img src="image_10.png" /><figcaption>**Fig. 6.** Absorption spectra of P(PBFA) electropolymerized films, plotted versus applied potential from –0.2 V to +1.2 V vs Ag/AgCl in 0.1 M LiTFSI in dry ACN, **a.** 2 cycles of electropolymerization, **b.** 3 cycles, **c.** 5 cycles and **d.** 10 cycles.</figcaption></figure>

Following the application of 1.2 V, the potential was switch back to 0 V for 110 seconds, during which the absorbance spectra changed back to their initial state (Figure S13). This reversible change in absorbance confirms the reversibility of the doping process, demonstrating the polymer ability to switch between doped and undoped states. Another method for p-type doping was studied by putting an additive at the surface of the film. For this purpose, we used the 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) which is one of the best-known dopants in organic electronics.46,47 Due to its low-lying LUMO, F4-TCNQ serves as an acceptor for a wide range of organic semiconductors. It works by extracting electrons from the HOMO of the semiconductor polymer, thereby inducing p-type doping. By increasing the number of charge carriers, the properties of the polymer can be modified and improved. For example, P. Pingel et al. studied the effect of F4-TCNQ doping on
P3HT and found that the conductivity of the semi-conductors increased from 8.10⁻⁵ S.m⁻¹ for P3HT alone to 1.10⁻³ S.m⁻¹ after deposition of F4-TCNQ.⁴⁸ In our study, we spin-coated a layer of F4-TCNQ (0.4 mg.mL⁻¹ in isopropanol) directly onto the electropolymerized P(PBFA) film. The effect of the doping agent was demonstrated by UV-Visible-NIR spectroscopy of the obtained film. Here again, we observed the appearance of a polaron band from 800 nm to 1400 nm which is indicative of P(PBFA) doping (Fig. 7.a). To confirm the effect of F4-TCNQ on P(PBFA), we performed UPS measurements on glass/ITO/P(PBFA) samples with and without F4-TCNQ. A slight shift of the HOMO (0.05 eV) and a reduction of the offset between the polymer HOMO and the Fermi level from 0.7 eV to 0.6 eV was observed for the doped polymer (Fig. 7.b). The UPS spectra of both doped and undoped P(PBFA) are available in the ESI (Figure S14). This is consistent with a p-doping of the polymer as was observed by Olthof et al.⁴⁹

<figure><img src="image_11.png" /><figcaption>**Fig. 7.** Study of the doping of P(PBFA) thin film (obtained after 2 electropolymerization cycles) with F4-TCNQ: **a.** UV-Visible-NIR spectra of the doped P(PBFA), **b.** Energy levels measured by UPS of P(PBFA) before and after doping by F4-TCNQ.</figcaption></figure>

In the following, we compared the stability of the two doping methods, electrochemical doping (via a 1.2 V potential application) and chemical doping (via F4-TCNQ by spin-coating), through kinetic monitoring. UV-Visible-NIR spectroscopy revealed that the
polaron band from electrochemical doping disappeared within one hour (Fig. 8.a), whereas the spectrum of the F4-TCNQ-doped film showed no significant change even after four days (Fig. 8.b). This demonstrates that chemical doping with F4-TCNQ is much more stable than electrochemical doping.

<figure><img src="image_12.png" /><figcaption>**Fig. 8.** Stability analysis of P(PBFA) polymer doping: a. Application of a 1.2 V vs Ag/AgCl potential for 220 s, spectra recorded between 0 and 1 h, b. Spin-coating of an F4-TCNQ solution on the polymer film, aging over 4 days.</figcaption></figure>

To investigate the potentiality of electropolymerized polymer films for organic electronic applications, P(PBFA) was introduced as the hole transport layer in organic photovoltaic (OPV) cells due to its deep HOMO level. The following architecture was used: Glass/ITO/P(PBFA)/PTQ10:Y6/Ca/Al. P(PBFA) films were electropolymerized on ITO using 1 and 2 cycles, yielding thicknesses of approximately 60 nm and 100 nm, respectively. Some of these films were subsequently doped via spin-coating with F4-TCNQ. After device fabrication, photovoltaic performances were evaluated using a solar simulator and under AM 1.5G conditions with a total irradiance of 1000 W/m². A power conversion of 2.3% was achieved for a device based on a doped film electropolymerized using a single cycle (Fig. 9). Doping the HTL lead to an improvement of the general performances of the OPV devices, compared to the undoped counterpart. In particular, the Voc for doped layer reach up to 0.79 V, close to the
reference device with PEDOT:PSS interlayer (0.81 V). This result suggests that P(PBFA) can act
as hole selective layer.

<figure><img src="image_13.png" /><figcaption>**Fig. 9.** Photovoltaic performance of OPV devices incorporating P(PBFA) as hole transport material. **a.** J–V characteristics of devices incorporating P(PBFA) electropolymerized in a single cycle, with and without F4-TCNQ doping. **b.** Comparison of J–V curves for devices without HTL, with PEDOT:PSS, and with P(PBFA) as the HTL.</figcaption></figure>

Interestingly, better photovoltaic performances, including J<sub>sc</sub> and power conversion efficiency PCE, were obtained when using electropolymerized films synthesized using a single cycle rather than two (Table 3). This improvement is likely due to a combination of factors. Thinner HTL facilitate hole extraction, while also minimizing parasitic absorption of incoming light by the deeply colored HTL, thereby allowing more photons to reach the active layer and generate charges.
<table><caption>**Table 3.** Photovoltaic performance of devices using P(PBFA) as the hole transport layer after one or two electropolymerization cycles, with or without chemical doping by F4-TCNQ, compared to reference devices incorporating PEDOT:PSS as HTL.</caption><thead><tr><th>Sample</th><th>J<sub>sc</sub><br>(mA/cm<sup>2</sup>)</th><th>V<sub>oc</sub><br>(V)</th><th>FF</th><th>PCE<br>(%)</th></tr></thead><tbody><tr><td>P(PBFA) 1 cycle</td><td>6.22</td><td>0.78</td><td>0.31</td><td>1.5</td></tr><tr><td>P(PBFA) 1 cycle doped</td><td>7.31</td><td>0.79</td><td>0.39</td><td>2.3</td></tr><tr><td>P(PBFA) 2 cycles</td><td>3.06</td><td>0.78</td><td>0.35</td><td>0.8</td></tr><tr><td>P(PBFA) 2 cycles doped</td><td>3.54</td><td>0.77</td><td>0.36</td><td>1.0</td></tr><tr><td>PEDOT:PSS</td><td>22.5</td><td>0.81</td><td>0.57</td><td>10.4</td></tr><tr><td>No HTL</td><td>4.09</td><td>0.03</td><td>0.49</td><td>0.06</td></tr></tbody></table>

Studies are ongoing to continue improving the electronic properties (charge transport, doping) of these electropolymerized HTL to improve the performances of OPV devices. Nevertheless, these preliminary results demonstrate the potential of using bio-sourced and electropolymerized polymers in organic electronic devices, opening new perspectives for the development of more sustainable materials in this field.

## Green metrics

The development of bio-based π-conjugated polymers for use as hole transport layers in OPV devices must combine synthetic innovation with environmental relevance, as they are intended to provide a sustainable energy technology. In our approach, several principles of green chemistry are embedded from the outset. The polymer is synthesized from furfural, a renewable furan derivative obtained from xylose, a sugar abundant in biomass. The precursor is prepared via a Knoevenagel condensation, a reaction known for its high atom efficiency, mild conditions, and minimal waste generation. Subsequently, the furfural-based precursors are electropolymerized directly onto the electrode surface, a process that avoids the use of additional chemical oxidants or metal catalysts, enables precise film formation in a single step, and minimizes solvent use and post-processing. Together, this strategy aligns with the concepts of waste prevention, safer synthesis and the use of renewable resources. To
complement these qualitative advances, we quantified the environmental performance of both the precursor synthesis and the electropolymerization step using standard green chemistry metrics (atom economy, E-factor, Process Mass Intensity) and life cycle assessment (LCA).

The atom economy of the Knoevenagel step leading to the PBFA precursor is high (92%), while the electropolymerization to form P(PBFA) reaches 100%, confirming that nearly all reactants are incorporated into the final products. However, as expected for early-stage laboratory syntheses, mass-based metrics are unfavorable. At laboratory scale, the E-factor and PMI of the PBFA synthesis were on the order of 300, while for the electropolymerization of P(PBFA) they reached nearly 950, mainly due to the large excess of solvents and electrolyte (LiTFSI) used. For comparison, industrial processes typically display E-factors in the range of 5–50 for fine chemicals and 25–100 for pharmaceuticals.⁵⁰ Although our values are high compared to industrial benchmarks, they remain in line with other laboratory-scale syntheses of π-conjugated polymers. For instance, Stille coupling routes have been reported with E-factors above 100 and, in some cases, exceeding 1000, largely due to solvent demand, stoichiometric metal reagents and multi-step purification.⁵¹,⁵² This highlights the need to optimize solvent and electrolyte use in our system and motivates the construction of a scale-up scenario with recovery strategies to enable meaningful comparison with industrially relevant processes. In this modeled scale-up scenario, which includes solvent and electrolyte recovery as well as process optimization, the metrics improve dramatically. The PMI of the PBFA synthesis decreases to ~4 and that of the electropolymerization to ~19, while the corresponding E-factors drop to ~3 and ~18. These values fall within or even below the typical range reported for fine-chemical processes, underscoring the potential of this route once recovery strategies are implemented.

While green metrics provide a first view of material efficiency, they remain mass-based and do not capture the nature of reagents or solvents, nor energy and infrastructure requirements.⁵³,⁵⁴ We therefore complemented them with an LCA, focusing here on the carbon footprint. At laboratory scale, the carbon footprint of the electropolymerization step to P(PBFA) is enormous, above 10,000 kg CO₂-eq per kg of polymer (Table S1-S2 and Figure S1-S2 and S5). This inflated value reflects the very low production scale (<1 g) and the
disproportionate influence of solvents and in particular, the LiTFSI electrolyte. Such results are
not directly benchmarkable, but they are consistent with the poor mass-based metrics
observed and clearly highlight the main contributors that must be optimized.

For the PBFA monomer, the modeled industrial-scale carbon footprint is around 30 kg CO₂-eq/kg of product, placing it within the range of specialty chemicals (Table S3 and Figure S3 and S6). Contribution analysis indicates that methanol use is the main driver but decreases significantly when recycling is included, while the contribution of furfural remains low, consistent with its biobased origin and relatively low carbon intensity. For the polymer P(PBFA), a modeled industrial scenario that includes solvent recovery and assumes either a reduction of electrolyte use to ~1 kg per kg of polymer or its recycling at rates above 90% leads to a footprint of about 100 kg CO₂-eq per kg (Table S4 and Figure S4 and S6). This value, which must be considered with caution given the uncertainties surrounding electrolyte management, remains higher than commodity polymers (≈2–3 kg CO₂-eq/kg) but falls into the broader range of specialty functional polymers.

Taken together, these results suggest that this synthetic route has environmental
promise: the PBFA monomer already shows an acceptable profile, and the polymer can
approach credible ranges provided electrolyte and solvent recovery are implemented. The
perspective is now to refine the scale-up modeling, extend the assessment beyond climate
change to multiple impact categories, and ultimately integrate the polymer into a full OPV
device LCA to benchmark it against other hole transport layers and, more broadly, against
other PV technologies.

Experimental part

**Chemical and Materials.** Furfural (ACS reagent, 99 %), p-phenylenediamine (≥ 99 %), tetrabutylammonium hydroxide (40 wt. % in water), dry acetonitrile (≥ 99.8 %, anhydrous), DMSO (ACS reagent, 99 %) and methanol (≥ 99.85 %) were purchased from Sigma-Aldrich. 1,4-phenylene diacetonitrile (> 98 %) was purchased from TCI. Dithiooxamide (98 %) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) (> 98 %) were purchased from Acros Organics. All reagents were used as received, without further purification.
**Synthesis of (2Z,2'Z)-2,2'-(1,4-phenylene)bis(3-(furan-2-yl)acrylonitrile) (PBFA).** Furfural (0.1 mL, 1.206 mmol, 1 eq.) and 1,4-phenylenediacetonitrile (0.16 g, 0.603 mmol, 0.5 eq.) were dissolved in 10 mL of methanol and heated in a microwave reactor (150 W) until 65 °C. Then, tetrabutylammonium hydroxide (0.78 mL, 1.206 mmol, 1 eq.) was carefully added to the medium. The solution was subjected to microwave radiation at 65 °C with a power of 150 W during 1 hour. The reaction kinetics were monitored by collecting aliquots from the crude reaction mixture at different time intervals and analyzing them by ¹H NMR in deuterated chloroform. A yellow solid was obtained and filtered using a Büchner funnel. The synthesized product was washed and recrystallized with methanol. Before the characterization, the solid product was dried under vacuum overnight (yield = 86 %). For the conventional synthesis, furfural and 1,4-phenylenediacetonitrile were added in the same quantities as for the microwave synthesis in methanol in a 100 mL Schlenk flask. The mixture was then heated to 65 °C, after which tetrabutylammonium hydroxide was carefully added. The reaction was maintained at 65 °C for 6 hours (yield = 75 %). Liquid ¹H nuclear magnetic resonance (NMR) spectra of the samples were recorded at 298 K using a 400 MHz Bruker Advance NMR in CDCl₃. ¹H NMR (400 MHz, CDCl₃, δ): 7.71 ppm (dd, 2H, H₃), 7.64 ppm (dd, 2H, -O-CH), 7.45 ppm (s, 2H, -CH=C-CN), 7.25 ppm (ddd, 4H, -C=CH-CH), 6.61 ppm (dd, 2H, -CH=CH-CH). HRMS calculated for C₂₀H₁₂N₂O₂: 312.33 g.mol⁻¹, found 312.089341 g.mol⁻¹. (Figure S7 and S11)

**Synthesis of (1E,1'E)-N,N'-(1,4-phenylene)bis(1-(furan-2-yl)methanimine) (PBFI).** Furfural (0.1 mL, 1.206 mmol, 1 eq.) and p-phenylenediamine (0.065 g, 0.603 mmol, 0.5 eq.) were dissolved in 10 mL of DMSO and heated in a microwave reactor at 100 °C with a power of 150 W for 1 hour. The reaction kinetics were monitored by ¹H NMR analysis of aliquots taken from the crude reaction mixture at different time intervals in deuterated chloroform. An orange solid was formed, which was filtered using a Büchner funnel. The obtained product was then washed and recrystallized with methanol. Prior to characterization, the solid was dried under vacuum overnight (yield = 83 %). For the conventional synthesis, furfural and p-phenylenediamine were used in the same quantities as in the microwave synthesis in DMSO in a 100 mL Schlenk flask. The reaction mixture was heated to 130 °C and maintained at that temperature for 18 hours (yield = 73 %). Liquid ¹H NMR spectra of the samples were recorded
at 298 K using a 400 MHz Bruker Avance NMR in DMSO-d<sub>6</sub>. <sup>1</sup>H NMR (400 MHz, DMSO-d<sub>6</sub>, δ): 8.80 ppm (s, 2H, -CH=N), 7.96 ppm (dd, 2H, -O-CH), 7.33 ppm (ddd, 4H, -H<sub>ar</sub>), 7.16 ppm (dd, 2H, -C=CH-CH), 6.73 ppm (dd, 2H, -CH=CH-CH). (<strong>Figure S9</strong>)

**Synthesis of 2,5-di(furan-2-yl)thiazolo[5,4-d]thiazole (BFTTz).** Furfural (0.1 mL, 1.206 mmol, 1 eq.) and dithiooxamide (0.0725 g, 0.603 mmol, 0.5 eq.) were dissolved in 10 mL of DMSO and added in a microwave vial to follow the same procedure as for the PBFI. A red solid was formed, which was filtered using a Büchner funnel. The obtained product was then washed and recrystallized with methanol. Prior to characterization, the solid was dried under vacuum overnight (yield = 80%). For the conventional synthesis, furfural and dithiooxamide were used in the same quantities as in the microwave synthesis in DMSO in a 100 mL Schlenk flask. The reaction mixture was heated to 130 °C and maintained at that temperature for 40 hours (yield = 73 %). Liquid <sup>1</sup>H nuclear magnetic resonance (NMR) spectra of the samples were recorded at 298 K using a 400 MHz Bruker Avance NMR in DMSO-d<sub>6</sub>. <sup>1</sup>H NMR (400 MHz, DMSO-d<sub>6</sub>, δ): 7.99 ppm (dd, 2H, -O-CH), 7.29 ppm (dd, 2H, -CH-CH-C-), 7.79 ppm (dd, 2H, -CH-CH-CH). (<strong>Figure S8 and S10</strong>)

**Electropolymerization of P(PFBA) and P(BFTTz).** To assess the electropolymerization potential of the precursors, cyclic voltammetry (CV) was conducted using a VersaSTAT3 potentiostat (Princeton Applied Research). CV data were collected in a solution containing 0.1 M LiTFSI in anhydrous acetonitrile, employing a scan rate of 50 mV.s<sup>-1</sup> ranging from 0 to +1.5 V vs Ag/AgCl. The experiments utilized a three-electrode setup, comprising an ITO (VisionTek Systems Ltd., 15 mm x 15 mm x 0.7 mm, 10 Ω.sq<sup>-1</sup>) substrate as the working electrode, a platinum wire counter electrode and an Ag/AgCl electrode in 3 mol.L<sup>-1</sup> KCl as the reference electrode. Prior to each electrochemical test, the working electrode surface was cleaned in an ultrasonic bath using several solutions: first, 10 minutes in a 4%w solution of Hellmanex basic soap, followed by three cycles of 5 minutes each in distilled water, and finally, 10 minutes in isopropanol.

**Spectroelectrochemistry of P(PBFA) polymer.** Electrochemical experiments were conducted in a three-electrode setup, using a solution of 0.1 M LiTFSI in dry acetonitrile. The electrochemical cell was positioned in the spectrometer (Cary 5000), with the light beam
passing through the polymer film. A series of potentials ranging from -0.2 V to +1.2 V was applied to the polymer film in 0.2 V increments, with each potential maintained for 110 seconds. During each 110-second interval, a UV-Visible-NIR spectrum of the film was recorded, allowing the monitoring of its optical evolution under electrochemical stimulation. Prior to any applied potential, the electropolymerized film exhibited a main absorption peak around 580 nm. As the potential increased stepwise from -0.2 V to +1.2 V, progressive changes in the UV-Visible-NIR spectra were observed.

**Organic photovoltaic cells fabrication.** Organic photovoltaic (OPV) devices were fabricated using a direct architecture: glass/ITO/P(PBFA)/PTQ10:Y6/Ca/Al. ITO-coated glass substrates (1.5 × 1.5 cm², 10 Ω/sq, VisionTek) were cleaned by sequential ultrasonic baths in diluted Hellmanex III solution, deionized water, and isopropanol. The hole transport layer, P(PBFA), was deposited by electropolymerization *via* 1 or 2 cyclic voltammetry cycles, following the previously described procedure. The resulting films were thermally annealed in air at 100 °C for 10 minutes. The active layer solution was prepared by dissolving a PTQ10:Y6 blend (weight ratio 1:1.2, total concentration 20 mg.mL⁻¹) in dry chloroform and stirring overnight at 55 °C in a nitrogen-filled glovebox. The solution was then filtered through a 0.45 µm PTFE filter and spin-coated (35 µL, 3000 rpm, 60 s) onto the P(PBFA) layer. A second thermal annealing step was performed at 100 °C for 10 minutes. Finally, calcium (20 nm) and aluminum (100 nm) electrodes were thermally evaporated under high vacuum (P = 10⁻⁶ mbar). The active area of the OPV devices was 10.5 mm².

**Current-Voltage characterization.** Current-voltage (J-V) characteristics were measured using a xenon solar simulator equipped with an AM 1.5G filter (Newport LCS-100), calibrated to a total irradiance of 1000 W.m⁻² (1-sun) using a certified silicon reference cell (Newport Co.). Measurements were carried out both in the dark and under simulated 1-sun illumination using a Keithley 2400 source-measure unit. Data acquisition and parameter extraction were performed automatically *via* a LabVIEW-based program. All J-V characterizations were conducted in a nitrogen-filled glovebox to minimize exposure to ambient atmosphere.

**Life Cycle Assessment methodology.** The environmental performance of the PBFA monomer and its electropolymerized polymer P(PBFA) was assessed by combining green chemistry metrics and life cycle assessment (LCA), based on a shared experimental inventory. Green
chemistry indicators (atom economy, E-factor and process mass intensity) were calculated following standard definitions.⁵⁰ The LCA was carried out in OpenLCA v2.4.1 with a functional unit of 1 kg of product, cradle-to-gate boundaries and the IMPACT World+ v2.0.1 method (footprint version).⁵⁵ Laboratory inventories included chemicals, solvents, energy use, single-use consumables and laboratory equipment (allocated over lifetime use). Industrial scenarios were extrapolated using the scale-up framework of Piccinno et al.,⁵⁶ explicitly incorporating solvent and electrolyte recovery. Background data were sourced from ecoinvent v3.10,⁵⁷ with additional datasets for consumables and incineration. Detailed inventories and extended results are provided in the Supporting Information.

## Conclusion

We successfully synthesized three furan-based precursors favoring microwave-assisted reactions, which offered significant advantages over traditional methods by improving reaction conditions such as reaction time, energy efficiency, and reproducibility. Microwave-assisted synthesis enhanced the yields of these precursors to 80%, compared to 70% obtained with conventional methods, setting the stage for the successful electrochemical polymerization of two bio-sourced π-conjugated polymers, P(PBFA) and P(BFTTz). These polymers were synthesized under mild conditions, enabling rapid and efficient polymerization without the need for harsh reagents or extreme temperatures. The electropolymerization technique not only facilitated the synthesis of the desired polymers but also allowed for the direct formation of homogeneous films on an ITO transparent conductive substrate. This aspect is particularly important for future applications, as it simplifies the fabrication process of electronic devices and ensures good adhesion of the polymer films to the substrate. The ability to form uniform films directly on the substrate without the need for additional processing steps is a key advantage in the development of organic electronic devices. In addition to the successful synthesis and film formation, the P(PBFA) polymer was further optimized through chemical doping with F4-TCNQ. The stable doping process is essential for applications where consistent performance is required over time, such as in organic photovoltaic cells and organic light-emitting diodes (OLEDs). Overall, this work highlights the potential of furan-based conjugated polymers, particularly P(PBFA), as promising materials for future organic electronic applications, notably supported by the
preliminary results obtained in organic photovoltaic devices using P(PBFA) as a hole transport layer. The combination of the use of bio-based precursors, efficient synthesis, easy film formation, and the ability to fine-tune the electronic properties of the polymers through doping opens new avenues for the development of more environmentally friendly organic devices. Finally, the comprehensive assessment of green metrics (atom economy, E-factor, PMI) together with the life cycle assessment of both precursor and polymer production demonstrates the markedly reduced environmental footprint of this approach compared to conventional π-conjugated polymer syntheses, reinforcing its potential as a benchmark for sustainable materials design in organic electronics.

Author contribution

H.R. conducted the majority of the experimental work, including the synthesis and characterization of the compounds (¹H NMR, UV-Vis), as well as electrochemical studies (electropolymerization, cyclic voltammetry, and spectroelectrochemistry), under the supervision of E.C. and C.B. H.R. also carried out the fabrication and characterization of the OPV devices under the guidance of L.V. and S.C. B.C.B. performed the AFM imaging of the electropolymerized films. P.L and I.D performed the calculation of the green metrics and the life cycle assessment. A.G., S.C., H.C., S.G., C.B., L.V., and E.C. contributed to the revision of the manuscript.

E-mail address corresponding authors: laurence.vignau@ims-bordeaux.fr, eric.cloutet@ubordeaux.fr
**Data availability**

The data supporting this article have been included as part of the ESI.

**Conflicts of interest**

There are no conflicts to declare.

**Supporting Information**

Green metrics methodology (E-factor, PMI and AE calculation), Life Cycle Assessment Methodology, LCI and process flow diagram for PBFA and P(PBFA) at laboratory and industrial scale, ¹H NMR of PBFA, BFTTz and PBFI, mass spectra of BFTTz and PBFA, cyclic voltrammetry of the precursors PBFI, PBFA and BFTTz, absorption spectra of electropolymerized P(PBFA) after 2, 3, 5 and 10 cycles of electropolymerization, UPS spectra of P(PBFA) doped and undoped, TGA of BFTTz, P(BFTTz), PBFA and P(PBFA) and DSC of P(BFTTz) and P(PBFA).

**Acknowledgements**

H.R. gratefully acknowledges financial support from the French Ministry of Higher Education and Research (MESRI) in the frame of interdisciplinary PhD fellowship from University of Bordeaux. This work was also supported by the French National Research Agency under the BIOCOP project (ANR-23-CE25-0020). H.R. would like to thank Roland Lefèvre and team of the ELORPrintTec facility for performing the SEM imaging and UPS measurements.
References

(1) Giraud, L.; Grelier, S.; Grau, E.; Hadziioannou, G.; Brochon, C.; Cramail, H.; Cloutet, E. Upgrading the Chemistry of π-Conjugated Polymers toward More Sustainable Materials. *J. Mater. Chem. C* **2020**, *8* (29), 9792–9810. https://doi.org/10.1039/d0tc01645d.

(2) Garbay, G.; Giraud, L.; Gali, S. M.; Hadziioannou, G.; Grau, E.; Grelier, S.; Cloutet, E.; Cramail, H.; Brochon, C. Divanillin-Based Polyazomethines: Toward Biobased and Metal-Free π-Conjugated Polymers. *ACS Omega* **2020**, *5* (10), 5176–5181. https://doi.org/10.1021/acsomega.9b04181.

(3) Pachariyangkun, A.; Suda, M.; Hadsadee, S.; Jungsuttiwong, S.; Nalaoh, P.; Pattanasattayavong, P.; Sudyoadsuk, T.; Yamamoto, H. M.; Promarak, V. Effect of Thiophene/Furan Substitution on Organic Field Effect Transistor Properties of Arylthiadiazole Based Organic Semiconductors. *J. Mater. Chem. C* **2020**, *8* (48), 17297–17306. https://doi.org/10.1039/D0TC04982D.

(4) Lee, S. M.; Lee, H. R.; Han, A.-R.; Lee, J.; Oh, J. H.; Yang, C. High-Performance Furan-Containing Conjugated Polymer for Environmentally Benign Solution Processing. *ACS Appl. Mater. Interfaces* **2017**, *9* (18), 15652–15661. https://doi.org/10.1021/acsmami.7b04014.

(5) Gidron, O.; Diskin-Posner, Y.; Bendikov, M. α-Oligofurans. *J. Am. Chem. Soc.* **2010**, *132* (7), 2148–2150. https://doi.org/10.1021/ja9093346.

(6) Woo, C. H.; Beaujuge, P. M.; Holcombe, T. W.; Lee, O. P.; Fréchet, J. M. J. Incorporation of Furan into Low Band-Gap Polymers for Efficient Solar Cells. *J. Am. Chem. Soc.* **2010**, *132* (44), 15547–15549. https://doi.org/10.1021/ja108115y.

(7) Wang, Y.; Yang, F.; Liu, Y.; Peng, R.; Chen, S.; Ge, Z. New Alkylfuranyl-Substituted Benzo[1,2-b:4,5-B']Dithiophene-Based Donor-Acceptor Polymers for Highly Efficient Solar Cells. *Macromolecules* **2013**, *46* (4), 1368–1375. https://doi.org/10.1021/ma3025738.

(8) Zhou, W.; Yu, C.; Chen, H.; Jia, T.; Zhang, W.; Yu, G.; Li, F. Improving the Photovoltaic Performance of Polymer Solar Cells Based on Furan-Flanked Diketopyrrolopyrrole Copolymers via Tuning the Alkyl Side Chain. *J. Phys. Chem. C* **2016**, *120* (9), 4824–4832. https://doi.org/10.1021/acs.jpcc.6b00890.

(9) Peleteiro, S.; Garrote, G.; Santos, V.; Parajó, J. C. Furan Manufacture from Softwood Hemicelluloses by Aqueous Fractionation and Further Reaction in a Catalyzed Ionic Liquid: A Biorefinery Approach. *J. Clean. Prod.* **2014**, *76*, 200–203. https://doi.org/10.1016/j.jclepro.2014.04.034.

(10) Caes, B. R.; Teixeira, R. E.; Knapp, K. G.; Raines, R. T. Biomass to Furanics: Renewable Routes to Chemicals and Fuels. *ACS Sustain. Chem. Eng.* **2015**, *3* (11), 2591–2605. https://doi.org/10.1021/acssuschemeng.5b00473.

(11) Gandini, A.; Lacerda, T. M.; Carvalho, A. J. F.; Trovatti, E. Progress of Polymers from Renewable Resources: Furans, Vegetable Oils, and Polysaccharides. *Chem. Rev.* **2016**, *116* (3), 1637–1669. https://doi.org/10.1021/acs.chemrev.5b00264.

(12) Gidron, O.; Dadvand, A.; Sheynin, Y.; Bendikov, M.; Perepichka, D. F. Towards “Green” Electronic Materials. α-Oligofurans as Semiconductors. *Chem Commun* **2011**, *47* (7), 1976–1978. https://doi.org/10.1039/C0CC04699J.

(13) Oo, T. Z.; Mathews, N.; Tam, T. L.; Xing, G. C.; Sum, T. C.; Sellinger, A.; Wong, L. H.; Mhaisalkar, S. G. Investigation of Photophysical, Morphological and Photovoltaic
Behavior of Poly(p-Phenylene Vinylene) Based Polymer/Oligomer Blends. *Thin Solid Films* **2010**, *518* (18), 5292–5299. https://doi.org/10.1016/j.tsf.2010.04.115.

(14) Colladet, K.; Fourier, S.; Cleij, T. J.; Lutsen, L.; Gelan, J.; Vanderzande, D.; Huong Nguyen, L.; Neugebauer, H.; Sariciftci, S.; Aguirre, A.; Janssen, G.; Goovaerts, E. Low Band Gap Donor-Acceptor Conjugated Polymers toward Organic Solar Cells Applications. *Macromolecules* **2007**, *40* (1), 65–72. https://doi.org/10.1021/ma061760i.

(15) Cevik, E.; İlicali, D.; Egbe, D. A. M.; Günes, S. Bulk Heterojunction and Inverted Type Solar Cells Using a CN-PPV Derivative. *Sol. Energy Mater. Sol. Cells* **2012**, *98*, 94–102. https://doi.org/10.1016/j.solmat.2011.09.055.

(16) Yu, G.; Heeger, A. J. Charge Separation and Photovoltaic Conversion in Polymer Composites with Internal Donor/Acceptor Heterojunctions. *J. Appl. Phys.* **1995**, *78* (7), 4510–4515. https://doi.org/10.1063/1.359792.

(17) Greenham, N. C.; Moratti, S. C.; Bradley, D. D. C.; Friend, R. H.; Holmes, A. B. Efficient Light-Emitting Diodes Based on Polymers with High Electron Affinities. *Nature* **1993**, *365* (6447), 628–630. https://doi.org/10.1038/365628a0.

(18) Jiang, X. Z.; Liu, Y. Q.; Song, X. Q.; Zhu, D. B. Color-Tunable Polymeric Light-Emitting Diodes Based on Blend of CN-PPV and PVK. *Synth. Met.* **1997**, *91* (1–3), 311–313. https://doi.org/10.1016/S0379-6779(98)80049-0.

(19) Wei, C.; Zou, J.; Zhang, W.; Huang, J.; Gao, D.; Wang, L.; Liao, Y.; Yu, G. Novel Vinylene-Bridged Donor-Acceptor Copolymers: Synthesis, Characterization, Properties and Effect of Cyano Substitution. *Mater. Chem. Front.* **2017**, *1* (10), 2103–2110. https://doi.org/10.1039/C7QM00236J.

(20) Gabano, E.; Ravera, M. Microwave-Assisted Synthesis: Can Transition Metal Complexes Take Advantage of This “Green” Method? *Molecules* **2022**, *27* (13), 4249. https://doi.org/10.3390/molecules27134249.

(21) Kempe, K.; Becer, C. R.; Schubert, U. S. Microwave-Assisted Polymerizations: Recent Status and Future Perspectives. *Macromolecules* **2011**, *44* (15), 5825–5842. https://doi.org/10.1021/ma2004794.

(22) Gu, C.; Huang, N.; Chen, Y.; Qin, L.; Xu, H.; Zhang, S.; Li, F.; Ma, Y.; Jiang, D. π-Conjugated Microporous Polymer Films: Designed Synthesis, Conducting Properties, and Photoenergy Conversions. *Angew. Chem.* **2015**, *127* (46), 13798–13802. https://doi.org/10.1002/ange.201506570.

(23) (Nee Włodarczyk), K. C.; Karczewski, J.; Jasiński, P. Influence of Electropolymerization Conditions on the Morphological and Electrical Properties of PEDOT Film. *Electrochimica Acta* **2015**, *176*, 156–161. https://doi.org/10.1016/j.electacta.2015.07.006.

(24) Zhou, D.; Zhang, K.; Zou, S.; Li, X.; Ma, H. Conjugated Microporous Polymers: Their Synthesis and Potential Applications in Flexible Electrodes. *J. Mater. Chem. A* **2024**, *12* (28), 17021–17053. https://doi.org/10.1039/D4TA02085E.

(25) Mo, W.; Zhu, Z.; Kong, F.; Li, X.; Chen, Y.; Liu, H.; Cheng, Z.; Ma, H.; Li, B. Controllable Synthesis of Conjugated Microporous Polymer Films for Ultrasensitive Detection of Chemical Warfare Agents. *Nat. Commun.* **2022**, *13* (1), 5189. https://doi.org/10.1038/s41467-022-32878-w.

(26) Ma, H.; Chen, Y.; Li, X.; Li, B. Advanced Applications and Challenges of Electropolymerized Conjugated Microporous Polymer Films. *Adv. Funct. Mater.* **2021**, *31* (33), 2101861. https://doi.org/10.1002/adfm.202101861.

(27) Liu, H.; Wang, Y.; Mo, W.; Tang, H.; Cheng, Z.; Chen, Y.; Zhang, S.; Ma, H.; Li, B.; Li, X. Dendrimer-Based, High-Luminescence Conjugated Microporous Polymer Films for Highly
Sensitive and Selective Volatile Organic Compound Sensor Arrays. *Adv. Funct. Mater.* **2020**, *30* (13), 1910275. https://doi.org/10.1002/adfm.201910275.

(28) Panasyuk, T. L.; Mirsky, V. M.; Piletsky, S. A.; Wolfbeis, O. S. Electropolymerized Molecularly Imprinted Polymers as Receptor Layers in Capacitive Chemical Sensors. *Anal. Chem.* **1999**, *71* (20), 4609–4613. https://doi.org/10.1021/ac9903196.

(29) Zhao, M.; Zhang, H.; Gu, C.; Ma, Y. Electrochemical Polymerization: An Emerging Approach for Fabricating High-Quality Luminescent Films and Super-Resolution OLEDs. *J. Mater. Chem. C* **2020**, *8* (16), 5310–5320. https://doi.org/10.1039/C9TC07028A.

(30) Del-Oso, J. A.; Frontana-Uribe, B. A.; Maldonado, J.-L.; Rivera, M.; Tapia-Tapia, M.; Roa-Morales, G. Electrochemical Deposition of Poly[Ethylene-Dioxythiophene] (PEDOT) Films on ITO Electrodes for Organic Photovoltaic Cells: Control of Morphology, Thickness, and Electronic Properties. *J. Solid State Electrochem.* **2018**, *22* (7), 2025–2037. https://doi.org/10.1007/s10008-018-3909-z.

(31) Osaka, T.; Ogano, S.; Naoi, K.; Oyama, N. Electrochemical Polymerization of Electroactive Polyaniline in Nonaqueous Solution and Its Application in Rechargeable Lithium Batteries. *J. Electrochem. Soc.* **1989**, *136* (2), 306–309. https://doi.org/10.1149/1.2096626.

(32) Triantou, D.; Soulis, S.; Koureli, S.; De Sio, A.; von Hauff, E. Thiophene-Based Copolymers Synthesized by Electropolymerization for Application as Hole Transport Layer in Organic Solar Cells. *J. Appl. Polym. Sci.* **2013**, *127* (1), 585–592. https://doi.org/10.1002/app.37831.

(33) Zhang, T.; Gregoriou, V. G.; Gasparini, N.; Chochos, C. L. Porous Organic Polymers in Solar Cells. *Chem. Soc. Rev.* **2022**, *51* (11), 4465–4483. https://doi.org/10.1039/D2CS00123C.

(34) Shao, J.-Y.; Zhong, Y.-W. Toward Stable and Efficient Solar Cells with Electropolymerized Films. *ACS Sustain. Chem. Eng.* **2022**, *10* (41), 13555–13567. https://doi.org/10.1021/acssuschemeng.2c04916.

(35) Bhuiyan, M. M. H.; Hossain, M. I.; Alam, M. A.; Mahmud, M. M. Microwave Assisted Knoevenagel Condensation: Synthesis and Antimicrobial Activities of Some Arylidene-Malononitriles. *J. Chem.* **2012**, *02* (01).

(36) Trasatti, S. The Absolute Electrode Potential: An Explanatory Note: (Recommendations 1986). https://doi.org/10.1515/iupac.58.0011.

(37) Bredas, J.-L. Mind the Gap! *Mater Horiz* **2014**, *1* (1), 17–19. https://doi.org/10.1039/c3mh00098b.

(38) Bertrandie, J.; Han, J.; De Castro, C. S. P.; Yengel, E.; Gorenflot, J.; Anthopoulos, T.; Laquai, F.; Sharma, A.; Baran, D. The Energy Level Conundrum of Organic Semiconductors in Solar Cells. *Adv. Mater.* **2022**, *34* (35), 2202575. https://doi.org/10.1002/adma.202202575.

(39) Holze, R. Optical and Electrochemical Band Gaps in Mono-, Oligo-, and Polymeric Systems: A Critical Reassessment.1. *Organometallics* **2014**, *33* (18), 5033–5042. https://doi.org/10.1021/om500604z.

(40) Al-Azzawi, A. G. S.; Aziz, S. B.; Dannoun, E. M. A.; Iraqi, A.; Nofal, M. M.; Murad, A. R.; M. Hussein, A. A Mini Review on the Development of Conjugated Polymers: Steps towards the Commercialization of Organic Solar Cells. *Polymers* **2022**, *15* (1), 164. https://doi.org/10.3390/polym15010164.

(41) Trasatti, S. The Absolute Electrode Potential: An Explanatory Note: (Recommendations 1986), 2016. https://doi.org/10.1515/iupac.58.0011.

(42) García-Cabezón, C.; Godinho, V.; Pérez-González, C.; Torres, Y.; Martín-Pedrosa, F. Electropolymerized Polypyrrole Silver Nanocomposite Coatings on Porous Ti Substrates
with Enhanced Corrosion and Antibacterial Behavior for Biomedical Applications. *Mater. Today Chem.* **2023**, *29*, 101433. https://doi.org/10.1016/j.mtchem.2023.101433.

(43) Wu, E. C.; Salamat, C. Z.; Ruiz, O. L.; Qu, T.; Kim, A.; Tolbert, S. H.; Schwartz, B. J. Counterion Control and the Spectral Signatures of Polarons, Coupled Polarons, and Bipolarons in Doped P3HT Films. *Adv. Funct. Mater.* **2023**, *33* (19), 2213652. https://doi.org/10.1002/adfm.202213652.

(44) Kepska, K.; Jarosz, T.; Januszkiewicz-Kaleniak, A.; Domagala, W.; Lapkowski, M.; Stolarczyk, A. Spectroelectrochemistry of Poly(3-Hexylthiophenes) in Solution. *Chem. Pap.* **2018**, *72* (1), 251–259. https://doi.org/10.1007/s11696-017-0277-6.

(45) Lee, H.; Kim, J.; Ok, E.; Kim, S.; Cho, K. Photoactivated-Doping-Induced Structural Ordering in Conjugated Polymers via Solution-Mixing for High-Performance Organic Thermoelectrics. *Nano Energy* **2025**, *145*, 111434. https://doi.org/10.1016/j.nanoen.2025.111434.

(46) Xiong, Y.; Ye, L.; Gadisa, A.; Zhang, Q.; Rech, J. J.; You, W.; Ade, H. Revealing the Impact of F4-TCNQ as Additive on Morphology and Performance of High-Efficiency Nonfullerene Organic Solar Cells. *Adv. Funct. Mater.* **2019**, *29* (1), 1806262. https://doi.org/10.1002/adfm.201806262.

(47) Chen, Q.; Xu, X.; Bo, Z. Application of N-Type or p-Type Dopants in Organic Photovoltaics. *ChemSusChem* **2025**, *18* (10), e202402525. https://doi.org/10.1002/cssc.202402525.

(48) Pingel, P.; Neher, D. Comprehensive Picture of p -Type Doping of P3HT with the Molecular Acceptor F 4 TCNQ. *Phys. Rev. B* **2013**, *87* (11), 115209. https://doi.org/10.1103/PhysRevB.87.115209.

(49) Olthof, S.; Tress, W.; Meerheim, R.; Lüssem, B.; Leo, K. Photoelectron Spectroscopy Study of Systematically Varied Doping Concentrations in an Organic Semiconductor Layer Using a Molecular P-Dopant. *J. Appl. Phys.* **2009**, *106* (10), 103711. https://doi.org/10.1063/1.3259436.

(50) Sheldon, R. A. Metrics of Green Chemistry and Sustainability: Past, Present, and Future. *ACS Sustain. Chem. Eng.* **2018**, *6* (1), 32–48. https://doi.org/10.1021/acssuschemeng.7b03505.

(51) Calascibetta, A. M.; Mattiello, S.; Sanzone, A.; Facchinetti, I.; Sassi, M.; Beverina, L. Sustainable Access to π-Conjugated Molecular Materials via Direct (Hetero)Arylation Reactions in Water and under Air. *Molecules* **2020**, *25* (16), 3717. https://doi.org/10.3390/molecules25163717.

(52) Sheldon, R. A. The E Factor at 30: A Passion for Pollution Prevention. *Green Chem.* **2023**, *25* (5), 1704–1728. https://doi.org/10.1039/D2GC04747K.

(53) Lucas, E.; Martín, A. J.; Mitchell, S.; Nabera, A.; Santos, L. F.; Pérez-Ramírez, J.; Guillén-Gosálbez, G. The Need to Integrate Mass- and Energy-Based Metrics with Life Cycle Impacts for Sustainable Chemicals Manufacture. *Green Chem.* **2024**, *26* (17), 9300–9309. https://doi.org/10.1039/D4GC00394B.

(54) Blömer, J.; Maga, D.; Röttgen, J.; Wu, Z.; Hiebel, M.; Eilebrecht, S.; Jentsch, S.; Eggers, N. Assessment of Chemical Products and Processes: Green Metrics and Life Cycle Assessment – A Comparison. *Chem. Ing. Tech.* **2024**, *96* (5), 561–574. https://doi.org/10.1002/cite.202300229.

(55) Bulle, C.; Margni, M.; Patouillard, L.; Boulay, A.-M.; Bourgault, G.; De Bruille, V.; Cao, V.; Hauschild, M.; Henderson, A.; Humbert, S.; Kashef-Haghighi, S.; Kounina, A.; Laurent, A.; Levasseur, A.; Liard, G.; Rosenbaum, R. K.; Roy, P.-O.; Shaked, S.; Fantke, P.; Jolliet, O. IMPACT World+: A Globally Regionalized Life Cycle Impact Assessment Method. *Int. J.*
*Life Cycle Assess.* **2019**, *24* (9), 1653–1674. https://doi.org/10.1007/s11367-019-01583-0.

(56) Piccinno, F.; Hischier, R.; Seeger, S.; Som, C. From Laboratory to Industrial Scale: A Scale-up Framework for Chemical Processes in Life Cycle Assessment Studies. *J. Clean. Prod.* **2016**, *135*, 1085–1097. https://doi.org/10.1016/j.jclepro.2016.06.164.

(57) Wernet, G.; Bauer, C.; Steubing, B.; Reinhard, J.; Moreno-Ruiz, E.; Weidema, B. The Ecoinvent Database Version 3 (Part I): Overview and Methodology. *Int. J. Life Cycle Assess.* **2016**, *21* (9), 1218–1230. https://doi.org/10.1007/s11367-016-1087-8.