## 3 Results  
Scheme 1 displays the synthesis of PTzTBI, in which PTzTBI was synthesized using the distannylated Tz Tz monomer (**1**) and the dibrominated TBI monomer (**2**) via the Stille coupling reaction. PTzTBI was soluble in chloroform and chlorinated benzenes. The \(M_{\text{n}}\) of PTzTBI was found to be 44.0 kDa, which was sufficiently high for semiconducting polymers with a PDI of 2.0. Figure 2a shows the UV-vis absorption spectrum of the PTzTBI thin film. The absorption range of PTzTBI was approximately 500-700 nm. The absorption maxima (\(\lambda_{\text{max}}\)) were observed at 590 nm and 647 nm. The absorption edge (\(\lambda_{\text{edge}}\)) was determined to be 705 nm from the onset, which corresponded to an optical bandgap (\(E_{\text{g}}\)) of 1.73 eV. To investigate the \(E_{\text{HOMO}}\) and \(E_{\text{LUMO}}\), cyclic voltammetry was carried out (Figure 2b). \(E_{\text{HOMO}}\) and \(E_{\text{LUMO}}\) of the PTzTBI were \(-5.48\) and \(-3.20\) eV, which were found to be lower than most of the Tz Tz-based polymers and similar to those of the TBI-based polymers that offer electron transportation [21]. Transistor characteristics of the polymers were evaluated using devices with a top-contact, bottom-gate configuration fabricated by using PTzTBI thin films spin-coated from chlorobenzene solution onto octadecyltriethoxysilane (ODTS)-modified Si/SiO\({}_{2}\) substrates, which were subsequently annealed at 200 \({}^{\circ}\)C. Figure 3a,b depicts typical transfer and output curves of the PTzTBI device, respectively. Interestingly, PTzTBI functioned as ambipolar semiconductor, though \(E_{\text{LUMO}}\) was relatively high: it showed transistor response in both positive and negative bias. The hole and electron mobilities (\(\mu_{\text{h}}\) and \(\mu_{\text{e}}\)) of PTzTBI evaluated at the saturation regime were 0.02 and 0.01 cm\({}^{2}\) V\({}^{-1}\) s\({}^{-1}\), respectively, which are among the average values for semiconducting polymers. To the best of our knowledge, this is the first example showing electron transportation in Tz Tz-based polymers. Although the mobility values were slightly lower than the other Tz Tz-based polymers, the result indicates well-balanced ambipolar behavior that is crucial for realizing logic circuits. The ordering structure of PTzTBI in the thin film was investigated by the GLXD measurement. The 2D GLXD image of the PTzTBI film on SiO\({}_{2}\) substrate is shown in Figure 4a. The cross-sectional  
Figure 3: (**a**) Transfer curves (\(p\)-channel: \(V_{\text{d}}=-60\) V, n-channel: \(V_{\text{d}}=60\) V) and (**b**) out-put curves (\(p\)-channel: \(V_{\text{g}}=-60\)–20 V), n-channel: \(V_{\text{g}}=60\)\(\cdots\)\(-20\) V) of a PTzTBI-based field-effect transistor (OFET). Figure 2: (**a**) UV-vis absorption spectrum of PTzTBI in thin film. (**b**) Cyclic voltammgram of PTzTBI. profile cut from the 2D GIXD pattern along the \(q_{x}\) and \(q_{xy}\) is also depicted in Figure 4b upper and lower, respectively. Although diffractions corresponding to the lamellar and \(\pi-\pi\) stacking structure appeared on both the \(q_{x}\) and \(q_{xy}\) axes, the \(\pi-\pi\) stacking diffraction mainly appeared on the \(q_{x}\) axis. This texture indicates that PTzTBI mainly forms the face-on orientation, which is in general unfavorable for OFET devices, though the edge-on orientation still co-exists. The \(\pi\)-\(\pi\) stacking distance of 3.57 A (calculated by the diffraction at the \(q_{x}\) axis corresponding to the face-on orientation) was relatively short for semiconducting polymers. The crystallinity of the polymer was evaluated by calculating the coherence length of the lamellar (\(L_{\mathrm{I}}\)), and \(\pi\)-\(\pi\) stacking (\(L_{\pi}\)) structures were estimated from [PERSON]'s equation (\(L=2\pi\)/fwhm) [23; 24], where fwhm is the full width half-maximum of the diffraction peak, using the diffraction of face-on orientation.