Highly effective III-V solar cells by controlling the surface roughnesses

황선태,길범진,Alan Jiwan Yun,김진현,김제원,우형섭,박기민,박병우 한국물리학회 2020 Current Applied Physics Vol.20 No.7

An advanced approach to minimize the light loss was discussed for III-V solar cells, by controlling the roughnesses of the device surface. Adhesives with different viscosities were applied to bond the III-V solar cells with the supporting substrate before the epitaxial lift-off process. The surface roughness of the III-V solar cells with epoxy adhesive (Rrms = 15.4 nm) is one order of magnitude higher than that with acrylic adhesive (Rrms = 1.6 nm), due to the differences in viscosity, resulting from the spreadability while being hardened. This roughness has increased the reflectance in the wavelength between 650 and 900 nm, implying that this reflectance is influenced by the rear surface of the solar cell. The device performance of the double-junction solar cells (Ga0.5In0.5P- and GaAs- based) also reflects the effect of the reflectance. The solar cell with the epoxy adhesive exhibited ~2% increase of the conversion efficiency than that with the acrylic adhesive, mainly due to the increased current density. The integrated current density from the external quantum efficiency (EQE) also exhibited ~2% increase only in the bottom (GaAs-based) cell, corresponding to the higher reflectance for red and near-infrared wavelength ranges.

Electronic Traps and Their Correlations to Perovskite Solar Cell Performance via Compositional and Thermal Annealing Controls

Hwang, Taehyun,Yun, Alan Jiwan,Kim, Jinhyun,Cho, Duckhyung,Kim, Sangyeon,Hong, Seunghun,Park, Byungwoo American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.7

<P>Herein, underlying factors for enabling efficient and stable performance of perovskite solar cells are studied through nanostructural controls of organic-inorganic halide perovskites. Namely, MAPbI<SUB>3</SUB>, (FA<SUB>0.83</SUB>MA<SUB>0.17</SUB>)Pb(I<SUB>0.83</SUB>Br<SUB>0.17</SUB>)<SUB>3</SUB>, and (Cs<SUB>0.10</SUB>FA<SUB>0.75</SUB>MA<SUB>0.15</SUB>)Pb(I<SUB>0.85</SUB>Br<SUB>0.15</SUB>)<SUB>3</SUB> perovskites (abbreviated as MA, FAMA, and CsFAMA, respectively) are examined with a grain growth control through thermal annealing. FAMA- and CsFAMA-based cells result in stable photovoltaic performance, while MA cells are sensitively dependent on the perovskite grain size dominated by annealing time. Micro-/nanoscopic features are comprehensively analyzed to unravel the origin that is directly correlated to the cell performance with the applications of electronic-trap characterizations such as photoconductive noise microscopy and capacitance analyses. It is revealed that CsFAMA has a lower trap density compared to MA and FAMA through the analyses of 1/<I>f</I> noises and trapping/detrapping capacitances. Also, an open-circuit voltage (<I>V</I><SUB>oc</SUB>) change is correlated to the variation of trap states during the shelf-life test: FAMA and CsFAMA cells with the negligible change of <I>V</I><SUB>oc</SUB> over weeks exhibit trap states shifting toward the band edge, although the power-conversion efficiencies are clearly reduced. The origins that critically affect the solar cell performance through the characterizations of shallow/deep traps with additional mobile defects in the perovskite and interfaces are discussed.</P> [FIG OMISSION]</BR>

Recent Progress in Inorganic Hole Transport Materials for Efcient and Stable Perovskite Solar Cells

Bumjin Gil,Alan Jiwan Yun,Younghyun Lee,Jinhyun Kim,Byungho Lee,Byungwoo Park 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.5

Organic–inorganic hybrid perovskite solar cells (PSCs) are considered as one of the most promising emerging photovoltaicswith outstanding performance. However, the commonly used organic hole transport materials (HTMs) suffer fromheat-, light-, and bias-induced degradation along with defect diffusion and hygroscopic properties. To resolve these issuesin conventional HTMs, inorganic materials with superior chemical stability, high carrier mobility, and low cost have beendeveloped, demonstrating improved stability under rigorous conditions such as high temperature and long-term illumination. Understanding the properties of alternative inorganic HTMs is of prominent importance to realize more stable and efficientPSCs. This review summarizes the recent progresses in inorganic HTMs adopted in various device architectures, with theirremarkable achievements in efficiency and long-term stability.

Recent Progress in Carbon Electrodes for Efficient and Cost-Benign Perovskite Optoelectronics

Jihyun Kim,Alan Jiwan Yun,Byungwoo Park,Jinhyun Kim 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.3

With popularity of the perovskite optoelectronics, its material properties and device performances have been widely studied. However, the issues in cost management and continuous fabrication still hinder the commercialization of the perovskiteoptoelectronics. Especially, the conventional electrodes such as metal and transparent conducting oxide (TCO) have limitationsdue to the difficulties in fabrication which requires high temperature and vacuum processes, largely increasing the timeand cost. Therefore, carbon materials with high electric conductivity and favorable work function are recently being noticedas alternatives to the conventional electrodes since the carbon materials are abundant in nature and low in the fabricationcost. Therefore, carbon electrode for the perovskite optoelectronics is widely studied to replace the conventional electrode,and utilizing carbon as an electrode can be the alternative solution for a future electrode model. In this review, the recentprogress of carbon electrodes in perovskite optoelectronics and various applications will be discussed.

Efficient Type-II Heterojunction Nanorod Sensitized Solar Cells Realized by Controlled Synthesis of Core/Patchy-Shell Structure and CdS Cosensitization

Lee, Sangheon,Flanagan, Joseph C.,Kim, Jaewook,Yun, Alan Jiwan,Lee, Byungho,Shim, Moonsub,Park, Byungwoo American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.21

<P>Here, we report the successful application of core/patchy-shell CdSe/CdSe<SUB><I>x</I></SUB>Te<SUB>1-<I>x</I></SUB> type-II heterojunction nanorods (HNRs) to realize efficient sensitized solar cells. The core/patchy-shell structure designed to have a large type-II heterointerface without completely shielding the CdSe core significantly improves photovoltaic performance compared to other HNRs with minimal or full-coverage shells. In addition, cosensitization with CdS grown by successive ionic layer adsorption and reaction further improves the power conversion efficiency. One-diode model analysis reveals that the HNRs having exposed CdSe cores and suitably grown CdS result in significant reduction of series resistance. Investigation of the intercorrelation between diode quality parameters, diode saturation current density (<I>J</I><SUB>0</SUB>) and recombination order (β = (ideality factor)<SUP>−1</SUP>) reveals that HNRs with open CdSe cores exhibit reduced recombination. These results confirm that the superior performance of core/patchy-shell HNRs results from their fine-tuned structure: photocurrent is increased by the large type-II heterointerface and recombination is effectively suppressed due to the open CdSe core enabling facile electron extraction. An optimized power conversion efficiency of 5.47% (5.89% with modified electrode configuration) is reported, which is unmatched among photovoltaics utilizing anisotropic colloidal heterostructures as light-harvesting materials.</P> [FIG OMISSION]</BR>

Multifunctional Green Solvent for Efficient Perovskite Solar Cells

Jaemin Cho,Beomsoo Kim,Seokjoo Ryu,Alan Jiwan Yun,Bumjin Gil,Jiheon Lim,Jihyun Kim,Jinhyun Kim,Byungwoo Park 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.5

Organometal trihalide perovskite has recently been considered as one of the leading candidates to achieve highly effi cient perovskite solar cells (PSCs). However, current PSC procedures commonly rely on the large volume of highly toxic halogenated or highly fl ammable solvents which are not favorable for the large-scale commercialization of PSCs. Herein, we employ nontoxic and nonhalogenated salicylaldehyde from the buckwheat as a both nonpolar (antisolvent) and polar (posttreatmentdissolving) solvent for the multifunctional purpose. Salicylaldehyde has a semipolar characteristic due to the hydroxyl group (–OH) attached to the benzene ring, enabling it to utilize both polar and nonpolar solvents in the PSCs fabrications. As a result, the PSC using green solvent achieved a power conversion effi ciency (PCE) up to 20.23%. Encapsulated devices retained over 80% of their initial PCE, after ~ 750 h of constant 1-sun illumination, and after ~ 1100 h under 60 °C heat. Overall, this work demonstrates that salicylaldehyde can be an alternative solvent for green and effi cient fabrication in the PSC.

Insights on the delithiation/lithiation reactions of Li_<i>x</i>Mn_0.8Fe_0.2PO₄ mesocrystals in Li⁺ batteries by <i>in situ</i> techniques

Wi, Sungun,Park, Jungjin,Lee, Sangheon,Kim, Jaewon,Gil, Bumjin,Yun, Alan Jiwan,Sung, Yung-Eun,Park, Byungwoo,Kim, Chunjoong Elsevier 2017 Nano energy Vol.39 No.-

<P><B>Abstract</B></P> <P>The kinetic processes during delithiation/lithiation of Li<SUB> <I>x</I> </SUB>Mn<SUB>0.8</SUB>Fe<SUB>0.2</SUB>PO<SUB>4</SUB> are thoroughly investigated through <I>operando</I> x-ray diffraction and <I>in situ</I> electrochemical impedance spectroscopy combined with galvanostatic intermittent titration technique (GITT), by which new insights on the phase propagation and sluggish kinetics of LiMn<SUB>0.8</SUB>Fe<SUB>0.2</SUB>PO<SUB>4</SUB> (LMFP) cathode materials are elaborated. <I>In situ</I> analyses on the solvothermally synthesized carbon-coated LMFP mesocrystals reveal that the phase-propagation mechanisms differ during delithiation/lithiation processes, and the sluggish kinetics of LMFP followed by the limitation of achievable (dis)charge capacities originate from the poor apparent Li<SUP>+</SUP> diffusivity, which is triggered by Mn redox reaction. Based on the in-depth characterization of the reaction kinetics in LMFP mesocrystals, our work provides fundamental understanding to design high-performance Mn-based olivine cathodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> LiMn<SUB>0.8</SUB>Fe<SUB>0.2</SUB>PO<SUB>4</SUB> mesocrystals synthesized by a straightforward solvothermal method. </LI> <LI> Superior electrochemical properties (i.e., high specific capacity and rate capability). </LI> <LI> Fundamental understanding on the reaction kinetics of LMFP by <I>in situ</I> techniques. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>