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Stable Perovskite Solar Cells with Improved Hydrophobicity Based on BHT Additive
Yuelong Huang,Yuelong Huang,Zhu Ma,Hanying Mao,Yuepeng Li,Hua Yu,Changtao Peng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.2
Remarkable progress has been achieved in organometallic halide perovskite solar cells (PSCs). However, poor environmental stability of PSCs has been proved to be challenging and needs further improvement. Here, a strategy of butylated hydroxytoluene (BHT) antioxidant additive with hydrophobic tert butyl and hydrophilic hydroxyl is developed to enhance the hydrophobicity, control nucleation rate and passivate the defect states of perovskite. The tert butyl group effectively prevents the penetration of moisture, as well as the formed hydrogen bond between hydroxyl group and iodine controls the assembly process of BHT and perovskite. By optimizing weight ratio of BHT and MAPbI3 in precursor solution, the power conversion efficiency of PSCs increased from 14.93% to 18.28% and greatly enhanced device stability compared with control device. We believe that our tactic of BHT additive can be applied to various perovskite films and will facilitate the realization of stable perovskite optoelectronics.
Yuelong Li,Linchuan Ma,유영석,Guangcai Wang,Xiaodan Zhang,고민재 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.73 No.-
A thin TiO2 layer is introduced by atomic layer deposition (ALD) onto the surface of TiO2 host-particles atlow-temperature, which serves as binding layer to enhance the interconnection of TiO2 hostnanoparticlesof photoelectrode or adhesion of photoelectrode with substrate. The power conversionefficiency of 4.63%, corresponding to 50% enhancement compared with 3.09% of reference cell, isachieved from ALD-treated cell. The electrochemical impedance spectroscopy confirms the reducedinternal resistance and much longer electron lifetime in ALD-treated cell. These results suggest that ALDtechnique can be used as an effective and precise technique to construct efficient dye-sensitized solarcells at low-temperature.
Yuelong Tang,Yuchun Hua 한국전산응용수학회 2013 Journal of applied mathematics & informatics Vol.31 No.3
In this paper, we investigate a priori error estimates and superconvergence of varitional discretization for nonlinear parabolic optimal control problems with control constraints. The time discretization is based on the backward Euler method. The state and the adjoint state are approximated by piecewise linear functions and the control is not directly discretized. We derive a priori error estimates for the control and superconvergence between the numerical solution and elliptic projection for the state and the adjoint state and present a numerical example for illustrating our theoretical results.
Tang, Yuelong,Hua, Yuchun The Korean Society for Computational and Applied M 2013 Journal of applied mathematics & informatics Vol.31 No.3
In this paper, we investigate a priori error estimates and superconvergence of varitional discretization for nonlinear parabolic optimal control problems with control constraints. The time discretization is based on the backward Euler method. The state and the adjoint state are approximated by piecewise linear functions and the control is not directly discretized. We derive a priori error estimates for the control and superconvergence between the numerical solution and elliptic projection for the state and the adjoint state and present a numerical example for illustrating our theoretical results.
A Maximum <i>a Posteriori</i> Estimation Framework for Robust High Dynamic Range Video Synthesis
Li, Yuelong,Lee, Chul,Monga, Vishal IEEE 2017 IEEE TRANSACTIONS ON IMAGE PROCESSING - Vol.26 No.3
<P>High dynamic range (HDR) image synthesis from multiple low dynamic range exposures continues to be actively researched. The extension to HDR video synthesis is a topic of significant current interest due to potential cost benefits. For HDR video, a stiff practical challenge presents itself in the form of accurate correspondence estimation of objects between video frames. In particular, loss of data resulting from poor exposures and varying intensity makes conventional optical flow methods highly inaccurate. We avoid exact correspondence estimation by proposing a statistical approach via maximum a posterior estimation, and under appropriate statistical assumptions and choice of priors and models, we reduce it to an optimization problem of solving for the foreground and background of the target frame. We obtain the background through rank minimization and estimate the foreground via a novel multiscale adaptive kernel regression technique, which implicitly captures local structure and temporal motion by solving an unconstrained optimization problem. Extensive experimental results on both real and synthetic data sets demonstrate that our algorithm is more capable of delivering high-quality HDR videos than current state-of-the-art methods, under both subjective and objective assessments. Furthermore, a thorough complexity analysis reveals that our algorithm achieves better complexity-performance tradeoff than conventional methods.</P>
Li, Yuelong,Lee, Doh-Kwon,Kim, Jin Young,Kim, BongSoo,Park, Nam-Gyu,Kim, Kyungkon,Shin, Joong-Ho,Choi, In-Suk,Ko, Min Jae The Royal Society of Chemistry 2012 Energy & environmental science Vol.5 No.10
<P>In this study, we developed a novel nanostructured polymer nanofiber/TiO<SUB>2</SUB> nanoparticle composite photoelectrode with high bendability by a spray-assisted electrospinning method. The composite film is used as the photoelectrode in plastic dye-sensitized solar cells (DSCs). The polymer/TiO<SUB>2</SUB> composite photoelectrode has a structure similar to that of a fiber-reinforced composite; the matrix of the composite photoelectrode contains TiO<SUB>2</SUB> nanoparticles, and PVDF nanofibers are embedded in this matrix. Compared to conventional DSCs, composite-based DSCs show outstanding bending stability because the polymer nanofibers prevent delamination of the electrode by relieving the external stress and effectively retarding crack generation and propagation. Moreover, the efficiency of the cell containing composite electrodes is comparable to that of a cell containing only TiO<SUB>2</SUB>, suggesting that the proposed PVDF-nanofiber-reinforced photoelectrode is a promising candidate for a bendable photoelectrode in high-efficiency flexible plastic DSCs.</P> <P>Graphic Abstract</P><P>We developed a novel nanostructured polymer nanofiber/TiO<SUB>2</SUB> nanoparticle composite photoelectrode with high bendability by a spray-assisted electrospinning method. The composite film is used as the photoelectrode in plastic dye-sensitized solar cells. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2ee21674d'> </P>
Li, Yuelong,Ma, Linchuan,Yoo, Youngseok,Wang, Guangcai,Zhang, Xiaodan,Ko, Min Jae Elsevier 2019 Journal of industrial and engineering chemistry Vol.73 No.-
<P><B>Abstract</B></P> <P>A thin TiO<SUB>2</SUB> layer is introduced by atomic layer deposition (ALD) onto the surface of TiO<SUB>2</SUB> host-particles at low-temperature, which serves as binding layer to enhance the interconnection of TiO<SUB>2</SUB> host-nanoparticles of photoelectrode or adhesion of photoelectrode with substrate. The power conversion efficiency of 4.63%, corresponding to 50% enhancement compared with 3.09% of reference cell, is achieved from ALD-treated cell. The electrochemical impedance spectroscopy confirms the reduced internal resistance and much longer electron lifetime in ALD-treated cell. These results suggest that ALD technique can be used as an effective and precise technique to construct efficient dye-sensitized solar cells at low-temperature.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Enhanced interconnection of TiO<SUB>2</SUB> nanoparticles by ALD-introduced thin TiO<SUB>2</SUB> layer. </LI> <LI> 50% increment in cell efficiency obtained in comparison with reference cells. </LI> <LI> Reduced internal resistance and enlarged electron life time confirmed by EIS. </LI> <LI> Potential of applying ALD to flexible devices on thermal-sensitive substrates. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Thin titania layer is prepared by atomic layer deposition (ALD) to enhance the interconnection of host titania nanoparticles for better performance of dye solar cells.</P> <P>[DISPLAY OMISSION]</P>
Li, Yuelong,Carretero-Palacios, Sol,Yoo, Kicheon,Kim, Jong Hak,Jimé,nez-Solano, Alberto,Lee, Chul-Ho,Mí,guez, Herná,n,Ko, Min Jae The Royal Society of Chemistry 2016 Energy & environmental science Vol.9 No.6
<P>We demonstrate that a combined optimization approach based on the sequential alternation of theoretical analysis and experimental realization gives rise to plastic supported dye solar cells for which both light harvesting efficiency and electron collection are maximized. Rationalized configurations with optimized light trapping and charge extraction are realized to achieve photoanodes on plastic prepared at low temperature, showing a power conversion efficiency of 8.55% and a short circuit photocurrent of 16.11 mA cm(-2), unprecedented for plastic based dye solar cell devices. Furthermore, the corresponding fully flexible designs present stable mechanical properties after several bending cycles, displaying 7.79% power conversion efficiency, an average broadband internal quantum efficiency above 90%, and a short circuit photocurrent of 15.94 mA cm(-2), which is the largest reported value for bendable cells of this sort to date.</P>
Li, Yuelong,Yoo, Kicheon,Lee, Doh-Kwon,Kim, Jin Young,Kim, Honggon,Kim, Bongsoo,Ko, Min Jae RSC Pub 2013 Nanoscale Vol.5 No.11
<P>An interparticle binding agent, or nanoglue, was synthesized by a sol-gel process, which facilitated the preparation of well-interconnected TiO2 electrodes at low-temperatures for plastic dye-sensitized solar cells. The viscosity of the nanoglue-based pastes was seven times higher than that obtained in pastes without any nanoglue. The increased viscosity was sufficiently high enough for coating thick films to fabricate TiO2 electrodes. The structural and photovoltaic properties of the films were extensively investigated by varying the amounts of nanoglue. A reduced pore size and greatly enhanced surface area were observed in the nanoglue-based films. Improved interparticle connectivity, resulting in faster electron transport, was confirmed by photocurrent transient spectroscopy and electrochemical impedance measurements of the nanoglue-based films. The electron diffusion length and charge collection efficiency were also enhanced in these nanoglue-based films. A maximum conversion efficiency of 5.43% was achieved in films containing 20 wt% nanoglue fabricated on a plastic substrate under one-sun illumination, even without any additional treatment.</P>