Novel stretchable <scp>light‐emitting</scp> diodes based on <scp>conjugated‐rod</scp> block <scp>elastic‐coil</scp> copolymers
Chih‐Chun Jao, Jiarui Chang, Chia‐Yu Ya, Wei‐Cheng Chen, Chia‐Jung Cho, Ja‐Hon Lin, Yu‐Cheng Chiu, Ye Zhou, Chi‐Ching Kuo
Abstract
In this study, we successfully fabricated an intrinsically stretchable light‐emitting diode (LED) by using a new conjugated rod–coil block copolymer, poly[2,7‐(9,9‐dioctylfluorene)]‐block‐poly(isoprene) (PF‐b‐PI). ( PF conjugated rods and PI coils exhibited fluorescent and intrinsically stretchable properties, respectively. Copolymers with three different rod/coil ratios, namely PF 18K ‐ b ‐PI 5K , PF 12K ‐ b ‐PI 5K and PF 12K ‐ b ‐PI 10K , were utilized for elastic LED demonstration. Notably, PF 18K ‐ b ‐PI 5K and PF 12K ‐ b ‐PI 5K LEDs can work under a strain of 140% because of suitable ratios of rod/coil lengths. Finally, a stretchable PF 12K ‐ b ‐PI 5K LED was measured with a low voltage of 2 V and with a brightness of 70 cd m −2 at 10 V. This LED was subjected to 100 cycles of luminance–strain testing under 50% strain and it maintained a stable level of brightness. These results demonstrated that the luminescent PF 12K ‐ b ‐PI 5K rod–coil block copolymers exhibit exceptional stretchability and high stability; these copolymers can be used in stretchable LEDs for a wide range of applications. © 2020 Society of Chemical Industry