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Enhancement of Light-Harvesting Ability on Perovskite Films via Preheated Substrates
오재원,이현복,류미이 한국진공학회 2023 Applied Science and Convergence Technology Vol.32 No.5
The fabrication of perovskite solar cells (PSCs) under ambient conditions is a major challenge for their commercialization. We evaluated the optical and device properties of the perovskite films in an uncontrolled environment through substrate preheating. The preheated substrate rapidly reached the turbid point and reduced the effect of relative humidity. An early antisolvent application time point with a preheated substrate increased the thickness of the perovskite film and improved its optical properties. However, the device characteristics were limited owing to the increased recombination with increasing thickness. Our results can guide the fabrication of high-quality, durable PSCs under various ambient conditions.
오재원,박성하,윤종찬,홍그루,이상학,강석민,최동훈 대한고혈압학회 2014 Clinical Hypertension Vol.20 No.2
Background: Obstructive sleep apnea (OSA) has been shown to be an important risk factor for metabolic syndrome andcardiovascular disease. Endothelial dysfunction plays a pivotal role in the pathophysiology of these diseases. However, littleis known about the relationship between sleep apnea and microvascular endothelial dysfunction, as assessed by digitalreactive hyperemia. Methods: The study population consisted of 80 patients (mean age, 48 ± 12 years-old; 65 men; 59hypertensive). We measured apnea–hypopnea index (AHI) and mild OSA was defined as 5 < AHI <15 and moderate tosevere OSA as AHI ≥ 15. Reactive hyperemia index (RHI) derived from peripheral arterial tonometry (PAT) asmeasurement of endothelium-mediated vasodilatation. Results: There were 61 OSA patients in the study population (AHI,21.5 ± 16.7 vs. 2.7 ± 1.6 in non-OSA; p < 0.001). There were no significant difference in RHI and peripheral augmentation index(pAIx) between OSA and non-OSA group (RHI, 2.04 ± 0.48 vs. 2.06 ± 0.42; p = 0.894; pAIx, 21.7% ± 24.0% vs. 21.7% ±30.0%; p = 1.000, respectively). Also, there was no significant difference in RHI and pAIx between mild (n = 31) andmoderate to severe (n = 30) OSA group (RHI, 2.10 ± 0.47 vs. 1.98 ± 0.49; p = 0.333; pAIx, 24.2% ± 20.7% vs. 19.0% ± 27.2%;p = 0.407, respectively), either. Overall, no significant correlation between AHI and RHI was observed (r = -0.023, p = 0.837). The other OSA severity indices such as oxygen desaturation index, mean and minimum oxygen saturation were not correlatedwith RHI or pAIx. In the subgroup analysis for the OSA group, we could not find any significant relationships between AHIand PAT parameters, either. Conclusions: OSA was not observed to be associated with reactive hyperemia measured by PAT.
다층 성장한 InAs/InAlGaAs 양자점의 광학적 특성
오재원,권세라,류미이,조병구,김진수,Oh, Jae-Won,Kwon, Se-Ra,Ryu, Mee-Yi,Jo, Byoung-Gu,Kim, Jin-Soo 한국진공학회 2011 Applied Science and Convergence Technology Vol.20 No.6
자발형성법으로 InP (001) 기판에 성장한 InAs/InAlGaAs 양자점(QDs, quantum dots)의 광학적 특성을 PL (photoluminescence)과 TRPL (time-resolved PL)을 이용하여 분석하였다. InAs 양자점 시료는 single layer InAs/InAlGaAs QDs (QD1)과 7-stacked InAs/InAlGaAs QDs (QD2)를 사용하였다. 저온(10 K)에서 QD1과 QD2 모두 1,320 nm에서 PL 피크가 나타났으며, 온도를 300 K까지 증가하였을 때 각각 178 nm와 264 nm의 적색편이(red-shift)를 보였다. QD1의 PL 소멸시간은 PL 피크인 1,320 nm에서 1.49 ns이고, PL 피크를 중심으로 장파장과 단파장으로 이동하면서 점차 짧아졌다. 그러나 QD2의 PL 소멸시간은 발광파장이 1,130 nm에서 1,600 nm까지 증가할 때 1.83 ns에서 1.22 ns로 점진적으로 짧아졌다. 이러한 QD2의 PL과 TRPL 결과는 평균 양자점의 크기가 InAs/InAlGaAs 층이 증가함에 따라 점차 증가하기 때문으로 single layer인 QD1에 비해 양자점 크기의 변화가 더 크기 때문으로 설명된다. Self-assembled InAs/InAlGaAs quantum dots (QDs) grown on an InP (001) substrate have been investigated by using photoluminescence (PL) and time-resolved PL measurements. The single layer (QD1) and seven stacks (QD2) of InAs/InAlGaAs QDs grown by the conventional S-K growth mode were used. The PL peak at 10 K was 1,320 nm for both QD1 and QD2. As the temperature increases from 10 to 300 K, the PL peaks for QD1 and QD2 were red-shifted in the amount of 178 and 264 nm, respectively. For QD1, the PL decay increased with increasing emission wavelength from 1,216 to 1,320 nm, reaching a maximum decay time of 1.49 ns at 1,320 nm, and then decreased as the emission wavelength was increased further. However, the PL decay time for QD2 decreased continuously from 1.83 to 1.22 ns as the emission wavelength was increased from 1,130 to 1,600 nm, respectively. These PL and TRPL results for QD2 can be explained by the large variation in the QD size with stacking number caused by the phase separation of InAlGaAs.