Yu, Hyeonggeun Nguyen, Tai LEE DO EUN Lee, Byung Chul Kim, Do Young 2024-01-12T06:35:09Z 2024-01-12T06:35:09Z 2023-07-13 2023-07 2637-6113 https://pubs.kist.re.kr/handle/201004/79880 Piezoelectric organic light-emitting diodes (p-OLEDs) are acousto-optic devices that enable direct visualization of ultrasound intensity profiles and pixel-free ultrasound imaging. However, there have been no reports since the initial report because the underlying physics has not been fully explained. In this study, we report the mechanism of p-OLEDs by elaborating on an alternating-current (AC)-driven operating environment. Strong light emission was observed from the p-OLED, although the ultrasound frequency (590 kHz) was significantly higher than the cutoff frequency (45 kHz) of our phosphorescent OLED. Such a contradictory result can be explained by an occurrence of a direct-current (DC) voltage offset or exceptionally large AC voltage generation in the OLED. We discovered that an AC voltage amplitude (VAC) as large as 16 V could be induced in the OLED by applying only 60 V of VAC to the transmitter, revealing the origin of the strong acousto-optical coupling, while the DC offset was not observed during the measurement. Based on this mechanism, we demonstrate that p-OLEDs made on the single-crystalline [Pb(Mg1/3Nb2/3)O3]1？x [PbTiO3]x substrate with a higher piezoelectric coefficient exhibit a considerably lower turn-on voltage and higher luminance compared to the case with the polycrystalline Pb(ZrxTi1？x)O3 substrate. English AMER CHEMICAL SOC Understanding the Mechanism of Piezoelectric Organic Light-Emitting Diodes Article 10.1021/acsaelm.3c00470 1 ACS Applied Electronic Materials, v.5, no.7, pp.3748 - 3755 ACS Applied Electronic Materials 5 7 3748 3755 N scie scopus 001026981000001 Engineering, Electrical & Electronic Materials Science, Multidisciplinary Engineering Materials Science Article piezoelectric organic light-emitting diode acousto-optic acoustic wave alternative-current