## 1 Introduction  
Organic semiconducting polymers have been extensively studied for their potential application in various electronic devices such as organic field-effect transistors, organic light-emitting diodes, photovoltaics, and sensors due to their unique properties such as light weight, large area solution processibility, varied optical bandgap, and mechanical flexibility [1; 2; 3; 4; 5; 6; 7; 8; 9]. Organic field-effect transistors (OFETs) have been developed as an alternative class of FETs that could be used in bioelectronic applications. Over the last two decades, significant improvements have been achieved through advanced molecular design, side-chain engineering, and device optimization [10; 11; 12; 13; 14]. Organic semiconducting polymers hold the edge over the conjugated small molecules when fabricating solution-based thin films due to the relatively high viscosity gained from the relatively high conjugation lengths [15; 16; 17; 18]. Among many factors that could be considered in developing polymeric backbones with improved intrinsic charge carrier mobility, solid-state molecular packing is essential, which has to be achieved by careful design of donor-acceptor alternating copolymers [19; 20; 21; 22; 23]. The donor-acceptor copolymer approach provides the advantage of mixing orbitals of donor-acceptor units, coupled alternately in \(\pi\)-conjugated polymer that eventually helps in tailoring the electronic bandgap of the material [24]. Out of many \(\pi\)-electron acceptors employed in OFETs, the diketopyrrolopyrrole (DPP) unit has been identified as one of the most efficient acceptor units due to its high unipolar ambipolar charge carrier mobilities associated with strong aggregation properties [25; 26; 27; 10; 22]. Apart from the \(\pi\)-electron acceptor, the selection of the \(\pi\)-electron donor is equally critical as it plays a significant role in adjusting inter/intramolecular interactions, hence benefitting molecular packing. Symmetric donor blocks, for example, e, are heavily utilized as electron-rich moieties to make regio-regular semiconducting polymers [28; 29]. However, in previous work reported by our group, we used the asymmetric donor, thieno[3,2-\(b\)]pyrrole (TP), which is an electron-rich versatile building block that also allows for an easy modification through \(N\)-alkylation reactions [26; 30; 31; 32; 33; 34; 35; 36]. Even though it was estimated that the pyrrole unit would be prone to oxidation, it was demonstrated that fused TP moiety is stable enough to realize OFET applications [31; 32; 26; 33]. Apart from the molecular backbone, side-chain density also plays a critical role in solution accessibility and charge transport by controlling the mesoscale assembly. The orientation of the side-chain attached to the backbone controls the local packing motifs and influences the electronic coupling between neighbor chains [37; 38]. Out of many modifications that could be performed to impart favorable electronic properties, donor-acceptor bridging unit improvements, i.e., spacer group improvements, tend to be more prominent as this unit changes the polymer backbone, which regulates charge transport [39; 40; 25; 41]. The furan spacer group is expected to provide smaller \(\pi\)-packing distances and better backbone planarity due to the small atomic size of oxygen, which is advantageous for charge-carrier transportation. Despite the main focus being on the OFET performance, one of the experimental observations that have drawn less attention is the non-linear behavior of the transfer curve observed for some high-performing organic semiconductors. Non-linear behavior often leads to an overestimation of charge carrier mobilities due to inaccurate data extraction [25; 42]. As a temporary solution, researchers now report mobilities extracted from both high and low voltages; however, which mobility is valid is still a question. This situation could be circumvented if we obtain \"nearly ideal\" transfer curves by molecular design to better estimate OFET performances [43; 26].