Highly bendable luminescent semiconducting organic single crystal

• Highly bendable luminescent semiconducting organic single crystals were demonstrated.
• DH-TTPTT single crystals were grown, and their crystal structure was solved.
• DH-TTPTT single crystals showed molecularly flat surfaces.
• The bending radius of the crystals was 0.2 mm corresponding to a bending strain of 5%.

Mechanical flexibility is one of the key benefits of organic electronics and optoelectronics. Although organic single crystals show the best performance in field-effect and light-emitting transistors, they are commonly considered to be brittle. In this work, we show that organic single crystals can be flexible, luminescent and semiconducting. We grew ∼1 cm-size single crystals of a thiophene/phenylene co-oligomer, 1,4-bis(5′-hexyl-2,2′-bithiene-5-yl)benzene, from solution and resolved their structure by x-ray analysis. The crystals were bendable with a radius down to 0.2 mm corresponding to a mechanical strain of 5%, had molecularly flat surface, showed the photoluminescence quantum yield up to 17% and charge mobility up to 0.07 cm2/Vs. Multiple bending cycles of the crystals did not affect their photoluminescence but resulted in minor degradation of the charge mobility. These findings indicate that organic single crystals can be a platform for flexible optoelectronic devices.

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