Research

Solution-processed organic semiconductors are attractive for flexible and large-area electronics because they are soft, lightweight and compatible with low-temperature fabrication. Our research aims to understand how molecular structure and packing govern charge transport, so that this knowledge can guide the development of improved materials and devices. We work closely with chemists and theorists to establish these structure–property relationships. For example, we showed that IDT-BT combines a near-amorphous microstructure with a planar, torsion-free backbone that is resilient to side-chain disorder, allowing its transport properties to approach intrinsic disorder-free limits [1].

Molecular model of a Ph-BTBT-C10 bilayer, showing phenyl bridges across the van der Waals gap and calculated charge redistribution.

We investigate how intermolecular coupling and molecular vibrations shape electronic behaviour across a wide temperature range, seeking design principles for improved charge transport in organic semiconductors [2].

Organic field-effect transistors provide a practical platform for relating microscopic charge transport to device performance. We investigate how semiconductor microstructure and energetics, electrode and dielectric interfaces, processing conditions and device architecture influence charge injection, transport and trapping, with their relative importance depending on the material and operating regime. For instance, we showed that, in high-mobility p-type conjugated polymers, water incorporated into nanometre-sized voids can cause charge trapping and device degradation, and that molecular additives which displace this water markedly improve operational and environmental stability [3].

Cross section of an IDT-BT OFET, with a top-gate, bottom-contact (TGBC) architecture.

We develop and study organic field-effect transistors to improve their reliability while retaining high charge carrier mobility, supporting their use in flexible electronics [4].

We extend our research to organic mixed ionic–electronic conductors, where electrochemical doping reaches carrier densities far beyond those accessible through field-effect gating alone. In this regime, interactions among carriers and between carriers and counterions become increasingly important. By controlling the doping level while measuring conductivity and thermopower, we investigate how these interactions reshape the density of states and influence transport. This allows us to probe the non-linear and non-equilibrium behaviour observed in strongly correlated systems [5].

IDT-BT OECT with an ion-gel electrolyte and integrated electrodes for conductivity and Seebeck coefficient measurements.

We use organic electrochemical transistors to prepare and probe otherwise inaccessible transport states, opening new routes to control the electrical properties of conducting polymers [6].

We investigate thermoelectric materials, whose performance is captured by the thermoelectric figure of merit, ZT, which depends on the Seebeck coefficient, electrical conductivity and thermal conductivity. Because these properties are interdependent, we study how molecular design, doping and processing can balance charge and heat transport in organic and low-dimensional materials. For instance, we showed that quasi-two-dimensional conjugated coordination polymers can combine defect-tolerant metallic electron transport with defect-sensitive phonon transport, allowing high electrical conductivity to coexist with exceptionally low lattice thermal conductivity [7].

Electrical conductivity and Seebeck coefficient of layered Ni-HATP plotted against inverse temperature, showing weakly temperature-dependent conductivity and a Seebeck coefficient that becomes less negative as temperature decreases.

We develop and characterise thermoelectric materials for a range of applications, including thermoelectric generators (TEGs) that convert waste heat into useful electrical power [8].

We investigate spin-dependent processes in organic semiconductors as a microscopic probe of charge transport. By combining field-induced and electrically detected electron spin resonance with transistor measurements, we can relate magnetic resonance signatures to device current and identify mechanisms that are difficult to resolve using electrical measurements alone. We study how carrier motion, trapping and molecular vibrations influence spin relaxation, and how these effects vary between different transport regimes. For instance, we showed that spin blockade can occur when mobile carriers encounter trapped charges along conducting pathways [9].

Electron spin-resonance spectra for a conjugated polymer, showing how the resonance near 3340 G changes with microwave field.

We use spin resonance to study carrier motion and spin relaxation in organic semiconductors. For example, comparing electron and hole polarons in the same ambipolar polymer reveals how wavefunction delocalisation and structural dynamics shape their behaviour [10].

We also apply our understanding of charge transport and device physics to emerging solution-processed semiconductors, including metal halide perovskites and conjugated coordination materials. In these systems, intrinsic behaviour can be obscured by ionic motion, trapping, hysteresis and contact resistance, making it essential to distinguish material properties from effects introduced by contacts and device operation. We therefore design devices and combine complementary measurements to identify the processes limiting performance and establish reliable measures of mobility, stability and switching. For example, we showed that reducing vacancy concentrations and ion migration can produce hysteresis-free, operationally stable perovskite field-effect transistors [11].

Tin-perovskite field-effect transistor mobility plotted against normalised drain-source voltage, comparing two-probe and four-probe measurements across the channel pinch-off regime.

We explore new semiconductor platforms for future electronics, identifying the advantages they offer and the challenges that must be overcome for practical devices [12].

  1. Venkateshvaran, D. et al. Approaching disorder-free transport in high-mobility conjugated polymers. Nature 515, 384–388 (2014).
  2. Lu, K. et al. Metallic charge transport in conjugated molecular bilayers. Nat. Electron. 9, 246–256 (2026).
  3. Nikolka, M. et al. High operational and environmental stability of high-mobility conjugated polymer field-effect transistors through the use of molecular additives. Nat. Mater. 16, 356–362 (2017).
  4. Nguyen, M. et al. Improving OFF-state bias-stress stability in high-mobility conjugated polymer transistors with an antisolvent treatment. Adv. Mater. 35, 2205377 (2023).
  5. Frisbie, C. D., Jacobs, I. E., Ren, X. & Sirringhaus, H. Charge transport physics of organic conductors at high carrier densities. Nat. Rev. Mater. 11, 437–452 (2026).
  6. Tjhe, D. H. L. et al. Non-equilibrium transport in polymer mixed ionic–electronic conductors at ultrahigh charge densities. Nat. Mater. 23, 1712–1719 (2024).
  7. Un, H.-I. et al. Defect-tolerant electron and defect-sensitive phonon transport in quasi-2D conjugated coordination polymers. Nat. Commun. 16, 6628 (2025).
  8. Un, H.-I. et al. Controlling film formation and host–guest interactions to enhance the thermoelectric properties of nickel–nitrogen-based 2D conjugated coordination polymers. Adv. Mater. 36, 2312325 (2024).
  9. Wang, Z. et al. Electrically detected magnetic resonance in ambipolar polymer field-effect transistors. Phys. Rev. Lett. 135, 166301 (2025).
  10. Carey, R. L. et al. Spin relaxation of electron and hole polarons in ambipolar conjugated polymers. Nat. Commun. 15, 288 (2024).
  11. Senanayak, S. P. et al. A general approach for hysteresis-free, operationally stable metal halide perovskite field-effect transistors. Sci. Adv. 6, eaaz4948 (2020).
  12. Zhang, Y. et al. Critical assessment of contact resistance and mobility in tin perovskite field-effect transistors. Adv. Electron. Mater. 11, e00924 (2025).