Development of Novel Carbazole- and Dibenzothiophene-based Organic Semiconductors and its application in Organic Field-Effect Transistors
[eng] In recent decades, electronic devices have become indispensable and have been subtly woven into the fabric of society. The growing demand for more advanced technologies requires the development of new semiconductors, which are the foundation of modern electronics. Although inorganics such as s...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/225047 |
| Acceso en línea: | https://hdl.handle.net/2445/225047 http://hdl.handle.net/10803/696171 |
| Access Level: | acceso embargado |
| Palabra clave: | Química orgànica Electrònica Semiconductors Transistors Organic chemistry Electronics |
| Sumario: | [eng] In recent decades, electronic devices have become indispensable and have been subtly woven into the fabric of society. The growing demand for more advanced technologies requires the development of new semiconductors, which are the foundation of modern electronics. Although inorganics such as silicon and germanium maintain a dominant role, they have intrinsic limitations that organic semiconductors (OSCs) can overcome, thanks to their structural modulability and compatibility with flexible and lightweight substrates. The performance of these devices depends on both the molecular properties (energy levels, packaging) and the processing conditions, which determine their morphology and crystallinity. In this context, the thesis studies semiconductors based on carbazole and dibenzothiophene (DBT) for organic field-effect transistors (OFETs) with the aim of correlating the molecular structure with the performance of devices and advancing the development of next-generation organic electronics. The triindole, derived from carbazole, was first investigated for its high potential as a hole transporter. N-alkylation allowed triindole derivatives to be obtained with chains from C2 to C12, subsequently being integrated into OFETs with various deposition architectures and techniques. For short chains, the resulting films were disordered, while substitution with hexyls proved to be optimal, with mobilities greater than 3 × 10⁻³ cm² V⁻¹ s⁻¹ in both vacuum evaporated and solution-processed devices. The deposition technique was decisive: vacuum evaporation favored medium chains, while bar-assisted meniscus shearing (BAMS) allowed operation with long chains, showing the complementarity between the two methods. Subsequently, peripheral alkyl substitution was introduced at the para and meta positions with respect to nitrogen. The substituted para-methyl triindole stood out as the best semiconductor, with mobilities of up to 4.7 × 10⁻³ cm² V⁻¹ s⁻¹. Otherwise, the lengthening of the chains or the substitution in the target position reduced mobility and gave rise to rougher morphologies and irregular crystalline domains. Beyond alkylation, triindoles and indolocarbazoles were functionalized with azobenzene (AB) chromophores to develop photoresponsive OFETs. Both the anchor position (No C-) and the number of AB units were varied. Time-of-flight measurements confirmed p-type behavior in AB-triindoles, with mobilities of up to 1.5 × 10⁻⁴ cm² V⁻¹ s⁻¹. However, additional AB units altered π–π stacking and reduced transport. AB-indolocarbazoles suffered from low solubility and deficient films, which made their manufacture difficult. Although the integration of these compounds is still preliminary, the results pave the way for the future development of photomodular OFETs. The last part of the thesis focused on the π extension of DBT derivatives through simple functionalizations, obtaining compounds with improved transport or emissive properties. All showed p-type behaviour, with mobilities of up to 8.3 × 10⁻⁵ cm² V⁻¹ s⁻¹. π extension and stiffening by cycle closure unlocked phosphorescence at room temperature (RTP) in Zeonex matrices, attributed to the reduction of singlet-triplet separation that facilitates crossover between systems. Functionalization modulated the balance of properties: phenanthre units favored mobility, while benzothiophene substituents enhanced RTP, with quantum yields of up to 14%. In some derivatives, the combination of RTP and intense blue fluorescence produced white light emission. Overall, the thesis shows how a precise molecular design, whether by alkylation, chromophore integration or π extension, directly governs the packaging, morphology, charge transport and emissive behavior of CSOs. By linking molecular design with device engineering, this work provides fundamental knowledge and practical guidelines to improve the performance and functionality of OFETs, paving the way towards flexible, economical and multifunctional organic devices. . |
|---|