A-π-D-π-A-Based Small Molecules for OTFTs Containing Diketopyrrolopyrrole as Acceptor Units

• Main Authors: Baji Shaik, Mujeeb Khan, Mohammed Rafi Shaik, Mohammed A.F. Sharaf, Doumbia Sekou, Sang-Gyeong Lee
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Micromachines
• Subjects: organic thin film transistors; hole mobility; small molecules; donor-acceptor; diketopyrrolopyrrole
• Online Access: https://www.mdpi.com/2072-666X/12/7/817
• ISSN: 2072-666X

A-π-D-π-A-based small molecules 6,6′-((thiophene-2,5-diylbis(ethyne-2,1-diyl))bis(thiophene-5,2-diyl))bis(2,5-bis(2-ethylhexyl)-3-(thiophen-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione) <b>(TDPP-T)</b> and 6,6′-(((2,3-dihydrothieno[3,4-b][1,4]dioxine-5,7-diyl)bis(ethyne-2,1-diyl))bis(thiophene-5,2-diyl))bis(2,5-bis(2-ethylhexyl)-3-(thiophen-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione) <b>(TDPP-EDOT)</b> have been designed and synthesized. The diketopyrrolopyrrole acts as an electron acceptor, while the thiophene or 3,4-ethylenedioxythiophene acts as an electron donor. The donor–acceptor groups are connected by an ethynyl bridge to further enhance the conjugation. The optoelectronics, electrochemical, and thermal properties have been investigated. Organic thin film transistor (OTFT) devices prepared from <b>TDPP-T</b> and <b>TDPP-EDOT</b> have shown p-type mobility. In as cast films, <b>TDPP-T</b> and <b>TDPP-EDOT</b> have shown a hole mobility of 5.44 × 10⁻⁶ cm² V⁻¹ s⁻¹ and 4.13 × 10⁻⁶ cm² V⁻¹ s⁻¹, respectively. The increase in the mobility of <b>TDPP-T</b> and <b>TDPP-EDOT</b> OTFT devices was observed after annealing at 150 °C, after which the mobilities were 3.11 × 10⁻⁴ cm² V⁻¹ s⁻¹ and 2.63 × 10⁻⁴ cm² V⁻¹ s⁻¹, respectively.