npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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Article

Research Paper

New Phys.: Sae Mulli 2019; 69: 806-812

Published online August 30, 2019 https://doi.org/10.3938/NPSM.69.806

Copyright © New Physics: Sae Mulli.

Investigation of Defects Generated During the Epitaxial Lift-off Process in a Flexible GaAs Solar Cell

Mo Geun SO1, Sang Jo LEE1, Hyun Jun JO1, Jong Su KIM*1, Thuy Thi NGUYEN2, Yeongho KIM2, Sang Jun LEE2, Heedae KIM3

1Department of Physics, Yeungnam University, Gyeongsan 38541, Korea

2Korea Research Institute of Standards and Science, Daejeon 34113, Korea
3School of Physics, Northeast Normal University, Changchun 130024, China

Correspondence to:jongsukim@ynu.ac.kr

Received: December 12, 2018; Revised: April 12, 2019; Accepted: April 12, 2019

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We have to investigate the optical and the electrical properties of flexible GaAs solar cells fabricated by using the epitaxial lift-off (ELO) process. Used the photoluminescence (PL) and J-V measurements. The as-grown GaAs solar cells were transferred onto Au/polyimide (ELO-layer/Au; ELA) and polydimethylsiloxane (PDMS) (ELO-layer/PDMS; ELP) flexible substrates. At 300~K, we observed PL emission bands caused by defects below the GaAs band edge transition energy (1.425~eV) for both the ELA and the ELP samples. The PL intensities for the ELA and the ELP samples, which were due to the defects in those samples, were higher than that for the as-grown sample. Moreover, the interference effect due to the internal multireflection (IMR) of PL light is lead that the PL peak by the defects is observed as the PL with several peaks. The PL intensity of the ELA sample was enhanced by the reflection effect at the GaAs/Au interface. In the J-V characteristics, the short-circuit current density and the efficiency of ELA sample were reduced by about 2.13~mA/cm$ ^{2}$ and 1.7\%, respectively, compared to the corresponding values for the GaAs-ref sample, because photo-generated carriers were trapped by the defect states generated during the ELO process.

Keywords: GaAs, Solar cell, Epitaxial lift-of, Defects

본 연구에서는 에피텍셜 리프트 오프 (Epitaxial lift-off; ELO) 공정이 적용된 GaAs 태양전지의 특성을 광발광 (photoluminescence; PL)과 전류밀도-전압(J-V) 측정으로 조사하였다. 성장된 GaAs 태양전지 시료(As-grown)를 Au/polyimide (ELO-layer/Au; ELA) 및 polydimethylsiloxane (PDMS)/glass (ELO-layer/PDMS; ELP) 기판들 위에 전사하였다. 300~K에서 ELA와 ELP시료들은 GaAs 띠 간 전이 에너지(1.425~eV) 보다 낮은 에너지에서 As-grown 시료와 비교하여 결함에 의한 PL 신호가 상대적으로 강하게 관측되었다. 이 때 결함에 의한 PL 신호들은 다수의 봉우리를 갖는 신호로 관측되었으며, 이는 내부 다중 반사(internal multi-reflection; IMR)에 의한 간섭 효과 때문이었다. ELA 시료의 경우에는 GaAs/Au 계면에 의한 반사 효과로 인하여 GaAs 띠 간 전이와 결함에 의한 PL 신호의 세기가 As-grown보다 증가하였다. 1 sun 에서 J-V 측정결과 ELA시료는 GaAs-ref 시료보다 단락전류와 태양전지 효율이 각각 2.13~mA/cm$ ^{2}$, 1.7\% 저하되었다. 이는 광 생성 운반자가 ELO 공정 중에 발생하는 결함에 의해 포획되기 때문이다.

Keywords: GaAs, Solar cell, Epitaxial lift-of, Defects

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