Open AccessEssential Role of Triplet Diradical Character for Large Magnetoresistance in Quinoidal Organic Semiconductor with High Electron Mobility
Author(s) -
Wang Chao,
Hao Hua,
Tajima Keisuke
Publication year - 2022
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202201045
Subject(s) - diradical , magnetoresistance , character (mathematics) , semiconductor , organic semiconductor , electron , materials science , electron mobility , electron transport chain , chemistry , photochemistry , optoelectronics , physics , magnetic field , singlet state , atomic physics , quantum mechanics , biochemistry , geometry , mathematics , excited state
Abstract A diradicaloid molecule with high semiconducting performance is synthesized based on the quinoidal benzo[1,2‐b:4,5‐b′]dithiophene structure. The diradical character is investigated by quantum chemical calculations and variable temperature electron spin resonance. The diode devices based on this molecule show a large change in electric current in magnetic fields below 100 mT with a strong dependence on the measurement temperatures; as the population of the triplet diradicals increases at high temperatures, the magnetoconductance (MC) values increase. As a result, a MC of −19.4% is achieved at 120 °C, which is the largest negative MC observed for organic molecules to date. In contrast, a smaller diradicaloid molecule based on quinoidal thieno[3,2‐b]thiophene without thermally accessible triplet state shows no MC, indicating the essential role of the triplet diradicals. The strong correlation between the MC and the triplet diradical concentrations suggests that the charge conduction in the diradicaloid is suppressed through a spin‐blocking mechanism, which can be controlled through the magnetic modulation of the hyperfine fields. The compound forms high‐crystallinity thin films and has high monopolar electron transport in organic field‐effect transistors, with an average mobility of 1.01 cm 2 V −1 s −1 for edge‐cast films.