Tuning phase separation in DPPDTT/PMMA blend to achieve molecular self-assembly in the conducting polymer for organic field effect transistors

Tahmina Afzal; M Javaid Iqbal; Badriah S Almutairi; Muhammad Zohaib; Muhammad Nadeem; Mohsin Ali Raza; Shahzad Naseem

doi:10.1063/5.0184290

Tuning phase separation in DPPDTT/PMMA blend to achieve molecular self-assembly in the conducting polymer for organic field effect transistors

J Chem Phys. 2024 Jan 21;160(3):034902. doi: 10.1063/5.0184290.

Authors

Tahmina Afzal¹, M Javaid Iqbal¹, Badriah S Almutairi², Muhammad Zohaib¹, Muhammad Nadeem¹, Mohsin Ali Raza³, Shahzad Naseem¹

Affiliations

¹ Centre of Excellence in Solid State Physics, University of the Punjab, Quaid-e-Azam Campus, Lahore 54590, Pakistan.
² Department of Physics, College of Science, Princess Nourah Bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia.
³ Department of Metallurgy and Materials Engineering, University of the Punjab, Lahore 54590, Pakistan.

PMID: 38230950
DOI: 10.1063/5.0184290

Abstract

The semiconductor/insulator blends for organic field-effect transistors are a potential solution to improve the charge transport in the active layer by inducing phase separation in the blends. However, the technique is less investigated for long-chain conducting polymers such as Poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (DPPDTT), and lateral phase separation is generally reported due to the instability during solvent evaporation, which results in degraded device performance. Herein, we report how to tailor the dominant mechanism of phase separation in such blends and the molecular assembly of the polymer. For DPPDTT/PMMA blends, we found that for higher DPPDTT concentrations (more than 75%) where the vertical phase separation mechanism is dominant, PMMA assisted in the self-assembly of DPPDTT to form nanowires and micro-transport channels on top of PMMA. The formation of nanowires yielded 13 times higher mobility as compared to pristine devices. For blend ratios with DPPDTT ≤ 50%, both the competing mechanisms, vertical and lateral phase separation, are taking place. It resulted in somewhat lower charge carrier mobilities. Hence, our results show that by systematic tuning of the blend ratio, PMMA can act as an excellent binding material in long-chain polymers such as DPPDTT and produce vertically stratified and aligned structures to ensure high mobility devices.