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Kim, Jun Young,Cho, Eunae,Kim, Jaehoon,Shin, Hyeonwoo,Roh, Jeongkyun,Thambidurai, Mariyappan,Kang, Chan-Mo,Song, Hyung-Jun,Kim, SeongMin,Kim, Hyeok,Lee, Changhee Optical Society of America 2015 Optics express Vol.23 No.19
<P>We demonstrate that nanocrystalline Al-doped zinc oxide (n-AZO) thin film used as an electron-extraction layer can significantly enhance the performance of inverted polymer solar cells based on the bulk heterojunction of poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) and [6,6]-phenyl C<sub>71</sub>-butyric acid methyl ester (PC<sub>70</sub>BM). A synergistic study with both simulation and experiment on n-AZO was carried out to offer a rational guidance for the efficiency improvement. As a result, An n-AZO film with an average grain size of 13 to 22 nm was prepared by a sol-gel spin-coating method, and a minimum resistivity of 2.1 ?? 10<sup>-3</sup> 곽·cm was obtained for an Al-doping concentration of 5.83 at.%. When an n-AZO film with a 5.83 at.% Al concentration was inserted between the ITO electrode and the active layer (PCDTBT:PC<sub>70</sub>BM), the power conversion efficiency increased from 3.7 to 5.6%.</P>
Kim, Jung Yong,Noh, Seunguk,Nam, Young Min,Kim, Jun Young,Roh, Jeongkyun,Park, Myeongjin,Amsden, Jason J.,Yoon, Do Y.,Lee, Changhee,Jo, Won Ho American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.11
<P>The effect of a nanoscale boron subphthalocyanine chloride (SubPc) interfacial layer on the performance of inverted polymer solar cells based on poly (3-hexyl thiophene) (P3HT) and [6,6]-phenyl-C<SUB>71</SUB>-butyric acid methyl ester (PC<SUB>71</SUB>BM) was studied. When a 1 nm SubPc layer was introduced between the active layer (P3HT:PC<SUB>71</SUB>BM) and MoO<SUB><I>x</I></SUB> in the device with ITO/ZnO/P3HT:PC<SUB>71</SUB>BM/SubPc/MoO<SUB><I>x</I></SUB>/Al configuration, the power conversion efficiency (PCE) was increased from 3.42 (without SubPc) to 3.59%. This improvement is mainly attributed to the enhanced open-circuit voltage from 0.62 to 0.64 V. When the Flory–Huggins interaction parameters were estimated from the solubility parameters through the contact angle measurement, it revealed that the interaction between SubPc and PC<SUB>71</SUB>BM is more attractive than that between SubPc and P3HT at the interface of P3HT:PC<SUB>71</SUB>BM/SubPc, through which charges are well transported from the active layer to the anode. This is supported by a decrease of the contact resistance from 5.49 (SubPc 0 nm) to 0.94 MΩ cm (SubPc 1 nm). The photoelectron spectra provide another evidence for the enhanced PCE, exhibiting that the 1 nm thick SubPc layer extracts more photoelectrons from the active layer than other thicknesses.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-11/am2009458/production/images/medium/am-2011-009458_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am2009458'>ACS Electronic Supporting Info</A></P>
Kim, Jaehoon,Jung, Heeyoung,Song, Jiyun,Kim, Kyunghwan,Lee, Changhee American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.28
<P>Stable and robust open-circuit voltage (V-oc) is essential to achieve a long lifetime for polymer solar cells (PSCs). Here, we investigate the Voc burn-in loss mechanism on the basis of the analysis of electroluminescence quantum efficiency (EQE(EL)) and impedance measurements in amorphous PSCs, with an inverted structure having different electron transport layers (ETLs) of ZnO nanoparticles (NPs) and the sol gel processed ZnO layer. We found that both charge recombination and energetic disorder account for a substantial proportion of the Voc burn-in loss. Moreover, varying the ETL significantly affected the degree of V-oc burn in loss, although relative contribution of these two factors remained constant. To accurately extract charge recombination induced V-oc loss, we applied a novel yet effective method that relates the EQEEL of PSCs to charge recombination-induced V-oc loss. Additional analyses, including those focused on light intensity (P-light)-dependent V-oc and density of states, will provide an inclusive perspective on the degradation mechanism of V-oc and development of stable PSCs.</P>
Changhee Shin,Namgue Lee,Hyeongsu Choi,Hyunwoo Park,Chanwon Jung,Seokhwi Song,Hyunwoo Yuk,Youngjoon Kim,Jong-Woo Kim,Keunsik Kim,Youngtae Choi,Hyungtak Seo,Hyeongtag Jeon 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.5
VO2 is an attractive candidate as a transition metal oxide switching material as a selection device for reduction of sneak-path current. We demonstrate deposition of nanoscale VO2 thin films via thermal atomic layer deposition (ALD) with H2O reactant. Using this method, we demonstrate VO2 thin films with high-quality characteristics, including crystallinity, reproducibility using X-ray diffraction, and X-ray photoelectron spectroscopy measurement. We also present a method that can increase uniformity and thin film quality by splitting the pulse cycle into two using scanning electron microscope measurement. We demonstrate an ON / OFF ratio of about 40, which is caused by metal insulator transition (MIT) of VO2 thin film. ALDdeposited VO2 films with high film uniformity can be applied to next-generation nonvolatile memory devices with high density due to their metal-insulator transition characteristic with high current density, fast switching speed, and high ON / OFF ratio.
Kim, Jae-Yup,Jang, Youn Jeong,Park, Jongwoo,Kim, Jeehye,Kang, Jin Soo,Chung, Dong Young,Sung, Yung-Eun,Lee, Changhee,Lee, Jae Sung,Ko, Min Jae Elsevier 2018 Applied Catalysis B Vol.227 No.-
<P><B>Abstract</B></P> <P>Among the various renewable sources of energy, solar energy conversion systems have been regarded as a promising way to satisfy the growing energy demand. For superior solar energy conversion performance, it is important to utilize efficient photosensitizers that have excellent light-harvesting capability. In this regard, quantum dots (QDs) are promising photosensitizer candidates owing to their high absorption coefficient, band gap tunability, and potential multiple exciton generation. Here, we report an effective and straightforward approach to improve the loadings of nanocomposite PbS/CdS QDs in a mesoporous electrode, for highly efficient solar energy conversion. By controlling the surface charge of TiO<SUB>2</SUB> during the successive ionic layer adsorption and reaction process, both the PbS and CdS QD loadings are distinctly increased, leading to a highly enhanced light-harvesting capability of the photoelectrodes. This enhancement is effectively applied not only for solar-to-electrical but also for solar-to-chemical energy conversion, resulting in a ∼33% increased conversion efficiency of the QD solar cells and an unprecedented photocurrent of 22.1 mA/cm<SUP>2</SUP> (at 0.6 V vs<I>.</I> RHE) for hydrogen production from photoelectrochemical water splitting. These results provide significant insight into the application of QD photosensitizers in solar energy conversion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PbS/Mn-doped CdS QDs were loaded on a mesoporous electrode. </LI> <LI> The QD loadings were increased by controlling the electrode surface charge. </LI> <LI> Due to the enhanced QD loadings, the efficiency of QD solar cells was increased by ∼33%. </LI> <LI> When applied in PEC water splitting, a remarkable photocurrent density of 22.1 mA/cm<SUP>2</SUP> was obtained. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>