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1. Benzobisthiadiazole-based high-spin donor–acceptor conjugated polymers with localized spin distribution

   https://doi.org/10.1039/D1MA00144B  

   Sabuj, Md Abdus; Huda, Md Masrul; Sarap, Chandra Shekar; Rai, Neeraj (May 2021, Materials Advances)

   null (Ed.)

   Stable organic semiconductors (OSCs) with a high-spin ground-state can profoundly impact emerging technologies such as organic magnetism, spintronics, and medical imaging. Over the last decade, there has been a significant effort to design π-conjugated materials with unpaired spin centers. Here, we report new donor–acceptor (D–A) conjugated polymers comprising cyclopentadithiophene and cyclopentadiselenophene donors with benzobisthiadiazole (BBT) and iso-BBT acceptors. Density functional theory calculations show that the BBT-based polymers display a decreasing singlet–triplet energy gap with increasing oligomer chain length, with degenerate singlet and triplet states for a N = 8 repeat unit. Furthermore, a considerable distance between the unpaired electrons with a pure diradical character disrupts the π-bond covalency and localizes the unpaired spins at the polymer ends. However, replacing the BBT acceptor with iso-BBT leads to a closed-shell configuration with a low-spin ground-state and a localized spin density on the polymer cores. This study shows the significance of the judicious choice of π-conjugated scaffolds in generating low- ( S = 0) and high-spin ( S = 1) ground-states in the neutral form, by modulation of spin topology in extended π-conjugated D–A polymers for emergent optoelectronic applications. 

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2. Beyond Integer Charge Transfer: A New Design Rule Linking Dopant Strength and Counterion Separation to Efficient Carrier Transport in Conjugated Polymers

   https://doi.org/10.1002/smll.75498  

   Duhandžić, Muhamed; Samanta, Subhayan; Venkataraman, Dhandapani; Akšamija, Zlatan (August 2026, Small)

   ABSTRACT Organic semiconductors, particularly conjugated polymers, are critical for advancing flexible electronics. Their electrical conductivity is enhanced by increasing carrier concentration through doping by blending small atoms or molecules, which can introduce Coulombic traps and disrupt packing. Here, we elucidate a molecular design principle that leverages dopant energy depth quantified by ΔE, which is the difference between appropriate frontier orbital energies of the doped polymer and its counterion, to mitigate disorder and simultaneously improve conductivity and the Seebeck coefficient. Using a modified Gaussian disorder model that incorporates carrier screening, we simulate the density of states and validate our findings experimentally with iodine‐ and Magic Blue‐doped poly(3‐hexylthiophene) (P3HT). Our results reveal that deeper dopant frontier energy levels significantly reduce energetic disorder and enhance transport properties when the carrier‐counterion separation is small. We identify a saddle‐point behavior in conductivity as a function of ΔEand show that ΔEcan significantly boost conductivity when the dopant is located close to the backbone. This work introduces ΔEas a powerful molecular lever for designing high‐performance organic semiconductors, offering a new design rule to overcome the long‐standing trade‐off between conductivity and Seebeck coefficient, thereby increasing thermoelectric efficiency in doped conjugated polymers. 

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3. Ground-State Charge-Transfer Doping Interactions in Donor–Acceptor Semiconducting Polymers

   https://doi.org/10.26434/chemrxiv-2025-g7tb5  

   Mahalingam, Paramasivam; Smith, Tanner; Balandin, Tanya; Gupta, Debapriya; Yu, Siqi; Dalal, Pushkar; Ng, Tse Nga; Flood, Amar Hugh; Danielsen, Scott_P O; Azoulay, Jason David (June 2025, ChemRxiv)

   Conjugated polymers are at the heart of numerous current and emerging technologies. Doping, a process by which charge carriers are introduced, is crucial to their functionality and performance. Despite significant historical context and the exploration of a broad chemical space, doping processes that are activated by formation of a ground-state charge-transfer complex (GS-CTC), which is mediated by the supramolecular hybridization between the frontier molecular orbitals of distinct molecular species, remain poorly understood. There are no clear demonstrations of this phenomena in contemporary donor–acceptor (DA) conjugated polymers (CP). Here, using diketopyrrolopyrrole-based donor–acceptor semiconducting polymers and a -conjugated penta-t-butylpentacyanopentabenzo[25]annulene “cyanostar” macrocycle, we demonstrate the first examples of features that control GS-CTC formation in contemporary DA CP frameworks. Using complementary experimental techniques and theory, we articulate how subtle molecular, electronic, and solid-state features impact supramolecular hybridization of the frontier molecular orbitals and impact the resultant (opto)electronic, magnetic, and transport properties. These studies demonstrate that subtle effects arising from the admixture between distinct -conjugated materials can have dramatic outcomes on properties and performance through modification of the density of states (DOS). These results will enable completely new design rules for organic semiconductors with precise property control. 

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4. A high-spin ground-state donor-acceptor conjugated polymer

   https://doi.org/10.1126/sciadv.aav2336  

   London, A. E.; Chen, H.; Sabuj, M. A.; Tropp, J.; Saghayezhian, M.; Eedugurala, N.; Zhang, B. A.; Liu, Y.; Gu, X.; Wong, B. M.; et al (May 2019, Science Advances)

   Interest in high-spin organic materials is driven by opportunities to enable far-reaching fundamental science and develop technologies that integrate light element spin, magnetic, and quantum functionalities. Although extensively studied, the intrinsic instability of these materials complicates synthesis and precludes an understanding of how fundamental properties associated with the nature of the chemical bond and electron pairing in organic materials systems manifest in practical applications. Here, we demonstrate a conjugated polymer semiconductor, based on alternating cyclopentadithiophene and thiadiazoloquinoxaline units, that is a ground-state triplet in its neutral form. Electron paramagnetic resonance and magnetic susceptibility measurements are consistent with a high-to-low spin energy gap of 9.30 × 10 −3 kcal mol −1 . The strongly correlated electronic structure, very narrow bandgap, intramolecular ferromagnetic coupling, high electrical conductivity, solution processability, and robust stability open access to a broad variety of technologically relevant applications once thought of as beyond the current scope of organic semiconductors. 

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5. Tunable Solid‐State Properties and Anisotropic Charge Mobility in Hydrogen‐Bonded Diketopyrrolopyrrole Polymers via Automated Device Fabrication and Characterization

   https://doi.org/10.1002/adfm.202403612  

   Nyayachavadi, Audithya; Wang, Chengshi; Vriza, Aikaterini; Wang, Yunfei; Ma, Guorong; Mooney, Madison; Mason, Gage T; Hu, Anita; Liu, Yuzi; Gu, Xiaodan; et al (October 2024, Advanced Functional Materials)

   Abstract The optoelectronic properties of semiconducting polymers and device performance rely on a delicate interplay of design and processing conditions. However, screening and optimizing the relationships between these parameters for reliably fabricating organic electronics can be an arduous task requiring significant time and resources. To overcome this challenge, Polybot is developed—a robotic platform within a self‐driving lab that can efficiently produce organic field‐effect transistors (OFETs) from various semiconducting polymers via high‐throughput blade coating deposition. Polybot not only handles the fabrication process but also can conduct characterization tests on the devices and autonomously analyze the data gathered, thus facilitating the rapid acquisition of data on a large scale. This work leverages the capabilities of this platform to investigate the fabrication of OFETs using hydrogen bonding‐containing semiconducting polymers. Through high‐throughput fabrication and characterization, various data trends are analyzed, and large extents of anisotropic charge mobility are observed in devices. The materials are thoroughly characterized to understand the role of processing conditions in solid state and electronic properties of these organic semiconductors. The findings demonstrate the effectiveness of automated fabrication and characterization platforms in uncovering novel structure–property relationships, facilitating refinement of rational chemical design, and processing conditions, ultimately leading to new semiconducting materials. 

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