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Shaheer Akhtar, M.,Choi, D.J.,Lee, S.K.,Yang, O.B. Elsevier 2010 Current Applied Physics Vol.10 No.2
A composite electrolyte for dye-sensitized solar cell (DSSC) was prepared with heteropolyacids (HPA) and polyethylene oxide (PEO) in the mixture solvent of chloroform and methanol. The amorphicity and ionic conductivity of the HPA-PEO composite electrolytes were significantly enhanced upon the appropriate dose of electron beam (e-beam) irradiation in the range of 40-120kGy. A DSSC fabricated with HPA-PEO irradiated at the optimum dose of 120kGy showed maximum overall conversion efficiency of 3.4% with a V<SUB>OC</SUB>of 0.588V, I<SUB>SC</SUB>of 9.68mA/cm<SUP>2</SUP>and fill factor of 58.9% under 100mW/cm<SUP>2</SUP> which improved by 13% efficiency in comparison with the DSSC with bare HPA-PEO composite electrolytes.
Thermally grown ZnO nanosheets for high efficiency dye-sensitized solar cells.
Akhtar, M Shaheer,Hyung, Jung-Hwan,Yang, O-Bong,Cho, Nam-Kyu,Hwang, Hak-In,Lee, Sang-Kwon American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.5
<P>High efficiency dye-sensitized solar cells (DSSCs) were fabricated using ZnO nanosheet electrodes. ZnO nanosheets were synthesized on top of fluorine-doped tin oxide (FTO) glass using Zn(OAc)2 as a precursor in the gold catalyzed chemical vapor deposition (CVD) method at a temperature of 800-900 degrees C. The synthesized materials were characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and Raman and photoluminescence (PL) spectroscopy. Typical DSSCs with ZnO nanosheets achieved moderately good conversion efficiency eta of approximately 2.12% with short-circuit current density J(SC) = 3.56 mA/cm2, open-circuit voltage V(OC) = 0.831 V, and fill factor FF = 71%. The high J(SC) and eta are attributed to high dye absorption through high surface ZnO nanosheets, which increased the light harvesting. The lower recombination rate was also observed in the ZnO nanosheet electrodes, resulting in high values of V(OC) and FF in the DSSCs.</P>
Akhtar, M.Shaheer,Lee, Hyun-Cheol,Min, Chun-Ji,Khan, M.A.,Kim, Ki-Ju,Yang, O-Bong 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.06
The effect of electron beam irradiation on dye sensitized solar cell (DSSC) has been studied to examine degradation of DSSC. The high-energy electron beam irradiation affects on the materials and performance of dye sensitized solar cells. We have checked the effects of electron beam irradiation of TiO₂ substrate with and without dye adsorption on the photovoltaic performances of resulting DSSCS and also studied the structural and electrical properties of polymers after irradiation. All solar cells materials were irradiated by electron beams with an energy source of 2MeV at different dose rates of 60 kGy, 120 kGy 240 kGy and 900 kGy and then their photoelectrical parameters were measured at 1 sun (100 mW/cm²). It was shown that the efficiency of DSSC was decreased as increasing the dose of e-beam irradiation due to lowering in TiO₂ crystallinity, decomposition of dye and oxidation of FTO glasses. On the other hand, the performance of solid-state DSSC with polyethylene oxide based electrolyte was improved after irradiation of e-beam due to enhancement of its conductivity and breakage of crosslinking.
M. Shaheer Akhtar,형정환,Dong-Joo Kim,양오봉,이상권,김태홍 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.3
We demonstrate for the first time novel perforated ZnO nanotube /TiO2 electrode-based dyesensitized solar cells (DSSCs). From the current-voltage characteristics, the open-circuit voltage VOC, short-circuit current density JSC, and the fill factor FF were determined to be ~0.84 V,~4.82 mA/cm2, and 0.60, respectively. We obtained a power conversion efficiency, η, of ~2.4%under air mass 1.5 global solar conditions. This represented an improvement of approximately 2 times as compared to ZnO nanowire/TiO2 electrode-based DSSCs. The superior photovoltaic performance and JSC value are attributed to high dye loading and high light harvesting via the high surface area of the ZnO nanotubes.
M. Shaheer Akhtar,Dae-Jin Choi,O-Bong Yang,이상권 한국물리학회 2010 Current Applied Physics Vol.10 No.2
A composite electrolyte for dye-sensitized solar cell (DSSC) was prepared with heteropolyacids (HPA) and polyethylene oxide (PEO) in the mixture solvent of chloroform and methanol. The amorphicity and ionic conductivity of the HPA–PEO composite electrolytes were significantly enhanced upon the appropriate dose of electron beam (e-beam) irradiation in the range of 40–120 kGy. A DSSC fabricated with HPA–PEO irradiated at the optimum dose of 120 kGy showed maximum overall conversion efficiency of 3.4% with a VOC of 0.588 V, ISC of 9.68 mA/㎠ and fill factor of 58.9% under 100 mW/㎠ , which improved by 13% efficiency in comparison with the DSSC with bare HPA–PEO composite electrolytes.
모하메드 샤히르 아크탈(Akhtar, M. Shaheer),박정근(Park, Jung-Guen),김의연(Kim, Ui-Yeon),이현철(Lee, Hyun-Choel),양오봉(Yang, O-Bong) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.11
In this work, polymer - inorganic composites have prepared using polymer such as polyethylene glycol (PEG)/poly (methyl methacrylate, PMMA) and inorganic nanofillers materials such as TiO2 nanotubes (TiNTs)/carbon nanotubes (CNTs). The extensive structural, morphological and ionic properties revealed that the high surface area and tubular feature of nanofillers improved the interaction and cross-linking to polymer matrix which is significantly enhanced the ionic conductivity and electrical properties of composite electrolytes. Comparably high conversion efficiency ~4.5% has been observed by using the newly prepared PEG-TiNTs composite solid electrolyte as compared with PMMA-CNTs electrolyte based DSSCs (~3%). The detailed comparative properties would be discussed in term of their structural, morphology, ionic and photovoltaic properties.
Ameen, Sadia,Akhtar, M. Shaheer,Nazim, M.,Kim, Eun-Bi,Nazeeruddin, Mohammad Khaja,Shin, Hyung-Shik Elsevier 2019 ELECTROCHIMICA ACTA Vol.319 No.-
<P><B>Abstract</B></P> <P>Inverted planar heterojunction solar cells (iPHSCs) were fabricated with novel spiro-bifluorene (CF-Sp-BTh) based hole transport material (HTM) and graphene oxide (GO) modified perovskite (CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>) as sensitizer. CF-Sp-BTh exhibited relatively high hole mobility and favorable HOMO level with respect to the valence band of CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>. iPHSC using CF-Sp-BTh HTM and GO (0.5 wt%)-CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> achieved the power conversion efficiency (PCE) of ∼14.28%, with open circuit voltage (V<SUB>OC</SUB>) of ∼1.07 V and a short circuit current density (J<SUB>SC</SUB>) of ∼18.82 mA/cm<SUP>2</SUP>. The photovoltaic performance of FTO/CF-Sp-BTh/GO (0.5 wt%)-CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB>/PC<SUB>61</SUB>BM/Au was higher compared to pristine CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> and other GO-CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> hybrid based devices. The photoluminescence decay and electrochemical impedance spectra confirmed an enhanced charge separation and retarded charge recombination of GO-CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> hybrid based iPHSCs.</P>
Cheng, Gang,Akhtar, M. Shaheer,Yang, O-Bong,Stadler, Florian J. American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.14
<P>An effective method was developed to prepare hybrid materials of TiO<SUB>2</SUB> nanoparticles on reduced graphene oxide (RGO) sheets for application in solar cells. The morphology, size, and crystal phase of the TiO<SUB>2</SUB> nanoparticles and TiO<SUB>2</SUB>@reduced graphene oxide (TiO<SUB>2</SUB>@RGO) hybrids were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), Raman, and UV-vis diffuse reflectance spectroscopy. A possible growth mechanism of TiO<SUB>2</SUB>@RGO hybrids is proposed based on observations of the TiO<SUB>2</SUB> nanoparticles obtained from the hydrolysis process under different conditions. The effects of different reduced graphene oxide contents on the energy conversion efficiency of the dye-sensitized solar cells (DSSCs) based on <I>J</I>–<I>V</I> and incident photon-to-current conversion efficiency (IPCE) spectra are also discussed. DSSCs based on TiO<SUB>2</SUB>@RGO hybrid photoanodes with a graphene content of 1.6 wt % showed an overall light-to-electricity conversion efficiency of 7.68%, which is much higher than that of pure anatase nanoparticles (4.78%) accompanied by a short-circuit current density of 18.39 mA cm<SUP>2</SUP>, an open-circuit voltage of 0.682 V, and a fill factor of 61.2%.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-14/am4013374/production/images/medium/am-2013-013374_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am4013374'>ACS Electronic Supporting Info</A></P>
형정환,M. Shaheer Akhtar,Dong-Joo Kim,양오봉,이상권 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
We report on ZnO nanowires (ZnO NWs), which were grown on the surface of a TiO2 thin-film electrode with zinc dihydrate acetate seeds by using thermal chemical vapor deposition. Detailed morphological properties revealed that the grown ZnO NWs fully covered the surface of the TiO2 thin-film electrode. The grown ZnO-NW-covered TiO2 thin films (ZnO NW/TiO2 thin-film) were used as working electrodes in dye-sensitized solar cells (DSSCs). We observed that a covering of ZnO NWs on the TiO2 thin-film electrodes improved the open-circuit voltage VOC and the fill factor FF while significantly decreasing the short-circuit current density JSC the and photovoltaic performance of the ZnO NW/TiO2 thin-film DSSCs compared to there for bare TiO2 thin-film DSSCs. The VOC and the FF of the ZnO NW/TiO2 thin-film based DSSCs were enhanced by about 10 − 15% compared to the values for bare TiO2 thin-film DSSCs. One can attribute the enhanced VOC and FF to the larger size of upstanding ZnO NWs on the TiO2 thin-film substrate, which slow surface recombination between the anode electrode and the electrolyte.