Suppression of Charge Recombination Rate in Nanocrystalline SnO₂ by Thin Coatings of Divalent Oxides in Dye-Sensitized Solar Cells

Lee, Chae-Hyeon,Lee, Gi-Won,Kang, Wee-Kyung,Lee, Doh-Kwon,Ko, Min-Jae,Kim, Kyoung-Kon,Park, Nam-Gyu Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.11

The core-shell $SnO_2$@AO (A=Ni, Cu, Zn and Mg) films were prepared and the effects of coatings on photovoltaic properties were investigated. Studies on X-ray photoelectron spectroscopy, energy dispersive X-ray analysis and transmission electron microscopy showed the formation of divalent oxides on the surface of $SnO_2$ nanoparticles. It was commonly observed that all the dye-sensitized core-shell films exhibited higher photovoltage than the bare $SnO_2$ film. Transient photovoltage measurements confirmed that the improved photovoltages were related to the decreased time constants for electron recombination.

Vapor transport deposited tin monosulfide for thin-film solar cells: effect of deposition temperature and duration

Lee, Dajeong,Cho, Jae Yu,Yun, Hee-Sun,Lee, Doh-Kwon,Kim, Taehoon,Bang, Kijoon,Lee, Yun Seog,Kim, Ho-Young,Heo, Jaeyeong Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.12

<P>The influence of the vapor transport deposition (VTD) conditions of tin sulfide (SnS) on the formation of secondary phases, preferred orientation, and solar cell performance is investigated in this study. It is concluded that 600 °C is the optimal growth temperature for the formation of pure SnS absorbers. When the growth temperature was 550 °C, the formation of secondary Sn2S3 and SnS2 phases was detected by Raman analysis. When the growth temperature was 625 °C, a noticeable change in morphology was observed with the plate-shaped grains aligned vertically to the substrate, which is detrimental to solar cell performance. The duration of growth also affected the morphology of the SnS absorber. Thin absorbers exhibited strong (120) preferred orientation. With increased duration of growth, (101) and (111) orientations increased. Such a variation in preferred orientation influenced the SnS/CdS solar cell’s performance. When the absorber thickness was as thin as ∼0.7 μm, the cell was prone to shunting and severe series resistance. When the absorber was as thick as ∼3.0 μm, physical shunting prevailed, worsening the performance of the cell. The highest efficiency of 3.93% with good cell-to-cell uniformity was achieved when the absorber thickness was ∼1.2 μm. The good stability of the best device was also confirmed under continuous illumination and damp-heat conditions for 100 h.</P>

Electron-Ion Interference and Onsager Reciprocity in Mixed Ionic-Electronic Transport inTiO2

Lee, Doh-Kwon,Yoo, Han-Ill American Physical Society 2006 Physical review letters Vol.97 No.25

Measurement of the Onsager coefficients of mixed ionic-electronic conduction in oxides

Lee, Doh-Kwon,Yoo, Han-Ill American Physical Society 2007 Physical review. B, Condensed matter and materials Vol. No.

Suppressed Formation of Conductive Phases in One-Pot Electrodeposited CuInSe₂ by Tuning Se Concentration in Aqueous Electrolyte

Lee, Byung-Seok,Park, Sung-Yul L.,Lee, Jang Mi,Jeong, Jeung-Hyun,Kim, Jin Young,Chung, Choong-Heui,Lee, Doh-Kwon American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.37

<P>The single-bath electrochemical deposition of CuInSe2 often leads to short-circuit behavior of the resulting solar cells due to,lhe high shunt conductance. In this, study, in amattemp't to resolve this problem, the influence of the Se precursor concentration (C-se) on electrodqpOsited CuInSe2 films and solar cell devices is examined in the C-Se range of 4.8 to 12:0 mM in selenite-based aqueous solutions ':containing Cu and In chlorides along with sulfarnic acid (H3NSO3) and potassium hydrogen phthalate (C8H5KO4) additives. As C-se increases,, the CuInSe2 layers become porous; and the grain, growth of the CuInSe2 phase is restricted,-while the parasitic shunting problem wag-markedly alleviated, as unambiguously demonstrated by measurements of the local current distribution. Due to these ambivalent influences, an optimal value of cse that achieves the best quality of the films for high-efficiency solar cells is identified. Thus, the.device prepared with 5.2 mM C-Se exhibits a power-conversion efficiency exceeding 10% with greatly improved device parameters, such as the shunt conductance and the reverse saturation current. The rationale of the present approach along-with the physicochemical,origin of its conspicuous impact on the resulting devices is discusSed in-conjunction with the electro-crystallization mechanism-of the CuInSe2 compound.</P>

Effect of Complexing/Buffering Agents on Morphological Properties of CuInSe₂ Layers Prepared by Single-Bath Electrodeposition

Lee, Hana,Lee, Wonjoo,Seo, Kyungwon,Lee, Doh-Kwon,Kim, Honggon Korea Photovoltaic Society 2013 Current Photovoltaic Research Vol.1 No.1

For preparing a device-quality $CuInSe_2$ (CISe) light-absorbing layer by single-bath electrodeposition for a superstrate-type CISe cell, morphological properties of the CISe layers were investigated by varying concentrations of sulfamic acid and potassium biphthalate, complexing/buffering agents. CISe films were grown on an $In_2Se_3$ film by applying a constant voltage of -0.5V versus Ag/AgCl for 90 min in a solution with precursors of $CuCl_2$, $InCl_3$, and $SeO_2$, and a KCl electrolyte. A dense and smooth layer of CISe could be obtained with a solution containing both sulfamic acid and potassium biphthalate in a narrow concentration range of combination. A CISe layer prepared on the $In_2Se_3$ film with proper concentrations of complexing/buffering agents exhibited thickness of $1.6{\sim}1.8{\mu}m$ with few undesirable secondary phases. On the other hand, when the bath solution did not contain either sulfamic acid or potassium biphthalate, a CISe film appeared to contain undesirable flake-shape $Cu_{2-x}Se$ phases or sparse pores in the upper part of film.

An EMF cell with a nitrogen solid electrolyte—on the transference of nitrogen ions in yttria-stabilized zirconia

Lee, Doh-Kwon,Fischer, Claus C.,Valov, Ilia,Reinacher, Jochen,Stork, Alexandra,Lerch, Martin,Janek, Juergen The Royal Society of Chemistry 2011 Physical chemistry chemical physics Vol.13 No.3

<P>The mobility and electrochemical activity of nitrogen inside and/or at the surface of ionic compounds is of fundamental, as well as of possibly practical, relevance. In order to better understand the role of nitrogen anions in solid electrolytes, we measured the transference number of nitrogen in yttria-stabilized zirconia (YSZ) by a concentration cell technique as a function of oxygen activity at different temperatures in the range of 1023 ≤<I>T</I>/<I>K</I>≤ 1123. YSZ doped with 1.9 wt% of N (YSZ:N) turned out to have an appreciable nitrogen transference number, which increased from 0 to 0.1 with decreasing oxygen activity in the range of −20 < log<I>a</I><SUB>O<SUB>2</SUB></SUB> < −14. The stability of N in YSZ:N, however, has yet to be elucidated under oxidizing conditions.</P> <P>Graphic Abstract</P><P>Solid state electrochemistry with (di-)nitrogen? EMF measurements with a zirconium oxide nitride (N-doped YSZ) solid electrolyte under reducing conditions reveal a significant transference number of nitrogen anions. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c003991h'> </P>

Crystallinity-Controlled Naphthalene-<i>alt</i>-diketopyrrolopyrrole Copolymers for High-Performance Ambipolar Field Effect Transistors

Lee, Hyo-Sang,Lee, Joong Suk,Cho, Sanghyeok,Kim, Hyunjung,Kwak, Kyung-Won,Yoon, Youngwoon,Son, Seon Kyoung,Kim, Honggon,Ko, Min Jae,Lee, Doh-Kwon,Kim, Jin Young,Park, Sungnam,Choi, Dong Hoon,Oh, Se Yo American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.50

<P>We report high-performance of ambipolar organic field-effect transistors (FETs) based on the low band gap copolymers of pDPPT2NAP-HD and pDPPT2NAP-OD. The polymers are composed of electron-rich 2,6-di(thienyl)naphthalene (T2NAP) and electron-deficient diketopyrrolopyrrole (DPP) units with branched alkyl chains of 2-hexyldecyl (HD) or 2-octyldodecyl (OD). The polymers were polymerized via Suzuki coupling, yielding optical band gaps of ∼1.4 eV. In the transistor performance test, we observed good ambipolar transport behavior in both polymer films, and pDPPT2NAP-OD displayed hole and electron mobilities 1 order of magnitude higher than the corresponding properties of pDPPT2NAP-HD. Thermal annealing of the polymer films increased the carrier mobilities. Annealing at 150 °C provided optimal conditions yielding saturated film crystallinity and maximized carrier mobility. The highest hole and electron mobilities achieved in these polymers were 1.3 and 0.1 cm<SUP>2</SUP>/(V s), respectively, obtained from pDPPT2NAP-OD. The polymer structure and thermal annealing affected the carrier mobility, and this effect was investigated by fully characterizing the polymer films by grazing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) experiments. The GIXD data revealed that both polymers formed highly crystalline films with edge-on orientation. pDPPT2NAP-OD, which included longer alkyl chains, showed a higher tendency to form long-range order among the polymer chains. Thermal annealing up to 150 °C improved the polymer film crystallinity and promoted the formation of longer-range lamellar structures. AFM and TEM images of the films were consistent with the GI-XD data. Theoretical calculations of the polymer structures provided a rationale for the relationship between the torsional angle between aromatic rings and the carrier mobility. From the intensive electrical measurements and full characterizations, we find that the chemical structure of polymer backbone and side alkyl chain has a profound effect on film crystallinity, morphology, and transistor properties.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-50/jp309213h/production/images/medium/jp-2012-09213h_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp309213h'>ACS Electronic Supporting Info</A></P>

Robust nanoscale contact of silver nanowire electrodes to semiconductors to achieve high performance chalcogenide thin film solar cells

Lee, Sangyeob,Lee, Jun Su,Jang, Jiseong,Hong, Ki-Ha,Lee, Doh-Kwon,Song, Soomin,Kim, Kihwan,Eo, Young-Joo,Yun, Jae Ho,Gwak, Jihye,Chung, Choong-Heui Elsevier 2018 Nano energy Vol.53 No.-

<P><B>Abstract</B></P> <P>We demonstrate the ability to fabricate high-quality nanoscale electrical contact between silver nanowires (AgNWs) and underlying semiconducting layers in chalcogenide thin film solar cells. AgNW electrodes have attracted many interests due to their ability for low temperature solution processing. However, they have a drawback that the interfacial defects can be generated between AgNWs and underlying rugged semiconductor layers making it difficult to form high-quality junction. To enhance the junction properties, conducting matrix layers have been adapted. Yet, the issues regarding the AgNW/semiconductor junction have not been fully resolved. We developed a facile method to form robust nanoscale contact between AgNWs and semiconducting thin films to achieve high performance chalcogenide thin film solar cells. The method is to deposit an ultra-thin semiconductor layer on devices using aqueous chemical bath deposition. The chemical bath deposition has capability to effectively fill even nanoscale gap and to form chemically stable bonds as well as an intimate junction. As a proof of concept, a CdS layer (~ 10 nm) was deposited using the chemical bath deposition on Cu(In,Ga)Se<SUB>2</SUB> (CIGS) solar cells with a structure of AgNW/CdS/CIGS/Mo/Glass. We also identified that the key factor governing the current-voltage characteristic is the electrical contact between the AgNW electrode and the CdS buffer layer in CIGS thin film solar cells. The power conversion efficiency of the CIGS cell was dramatically improved from 4.9% to 14.2% owing to high-quality AgNW-CdS electrical contact produced by chemical bath deposition of the additional CdS layer as thin as 10 nm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A facile method to form robust nanoscale contact between AgNWs and semiconductors for high performance solar cell. </LI> <LI> Formation of high quality junction between AgNWs and a CdS buffer layer in CIGS solar cells by chemical bath deposition. </LI> <LI> Due to the high quality contact, the efficiency of CIGS solar cells dramatically improves from 4.9% to 14.2%. </LI> <LI> The cells with high quality junction show high performance at any illumination conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of Complexing/Buffering Agents on Morphological Properties of CuInSe<SUB>2</SUB> Layers Prepared by Single-Bath Electrodeposition

Hana Lee,Wonjoo Lee,Kyungwon Seo,Doh-Kwon Lee,Honggon Kim 한국태양광발전학회 2013 Current Photovoltaic Research Vol.1 No.1

For preparing a device-quality CuInSe2 (CISe) light-absorbing layer by single-bath electrodeposition for a superstrate-type CISe cell, morphological properties of the CISe layers were investigated by varying concentrations of sulfamic acid and potassium biphthalate, complexing/buffering agents. CISe films were grown on an In2Se3 film by applying a constant voltage of -0.5V versus Ag/AgCl for 90 min in a solution with precursors of CuCl2, InCl3, and SeO2, and a KCl electrolyte. A dense and smooth layer of CISe could be obtained with a solution containing both sulfamic acid and potassium biphthalate in a narrow concentration range of combination. A CISe layer prepared on the In2Se3 film with proper concentrations of complexing/buffering agents exhibited thickness of 1.6~1.8 μm with few undesirable secondary phases. On the other hand, when the bath solution did not contain either sulfamic acid or potassium biphthalate, a CISe film appeared to contain undesirable flake?shape Cu2-xSe phases or sparse pores in the upper part of film.