[2014년 2학기 물리학과 콜로퀴엄]
연사: 임은주 교수 (단국대학교 응용물리학과)
제목: 2차 비선형 광학측정 및 전하변조분광기를 통한 유기물 반도체 전하이동연구
(Study of carrier transport mechanism of organic devices by charge modulation spectroscopy and electri-field induced optical second harmonic geneation mechanism)
초록:
유기반도체 소자의 전하이동 현상을 광학적 측정 (Time-resolved electric field induced optical second harmonic generation: TR-EFISHG), (Charge modulation spectroscopy: CMS), 그리고 맥스웰-와그너 모델링을 통해 분석하였다. TIPS-pentacene 유기물 층 내부의 전하 주입, 이동 및 트랩 현상을 직접적으로 관측하고, 이를 바탕으로 이론적 기반을 구축하였다. 광학측정을 이용한 전하관측 및 유전체 물리를 이용한 맥스웰-와그너 모델링 분석은 고효율 유기반도체 소자를 위해 제시하는 새로운 접근법이다. 이들 방법으로 유기반도체 소자의 구동 메커니즘을 가시화하여 명확히 분석할 수 있었다.
Organic semiconductors have been investigated for use along with an effort to achieve low cost, easy fabrication, and lots of application since the discovery of conducting materials. We can see typical examples in studies on organic field effect transistors, organic light emitting diodes, organic solar cells, and so forth, where many theoretical and experimental studies on carrier mechanisms have been carried out. However, these studies are still not sufficient for the use of organic semiconductors in actual organic devices. We therefore present a method for studying carrier motions in organic devices by using time-domain measurement and energetic measurement in combination. The measurement is based on charge modulation spectroscopy (CMS) in energetic measurement and time-resolved electric field induced optical second harmonic generation (TR-EFISHG) measurement. The TR-EFISHG measurement is very effective to directly measure electric field distributions and potential distributions in organic devices under operational conditions, and available for analyzing carrier motions on the basis of a Maxwell-Wagner model. The CMS is capable of probing energy states of carriers in organic materials.
In this study, by using this method, we studied the carrier transport mechanism in ITO/PI/TIPS-pentacene/Au diodes, in terms of the current-voltage and capacitance-voltage characteristics. Results give an insightful picture on the carrier injection, and the succeeding carrier accumulation and carrier transport, which cannot be obtained by the use of conventional I-V and C-V measurements. These results indicate that these measurements are very helpful for studying dynamic carrier effects of the real and energy spaces. Finally, we should note that TR-EFISHG can probe carrier trapping, anisotropic carrier behavior, etc., thus the detailed carrier transport mechanism in organic films including complex systems will be clarified by coupling with CMS measurement.
일시: 10월 2일 오후 4시 30분
장소: 베어드홀 103호
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