School of Chemistry

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Browsing School of Chemistry by Author "Abulikemu, Mutalifu"
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    Amorphous Tin Oxide as a Low-Temperature-Processed Electron-Transport Layer for Organic and Hybrid Perovskite Solar Cells
    ( 2017-04-05) Barbé, Jérémy ; Tietze, Max L. ; Neophytou, Marios ; Murali, Banavoth ; Alarousu, Erkki ; Labban, Abdulrahman El ; Abulikemu, Mutalifu ; Yue, Wan ; Mohammed, Omar F. ; McCulloch, Iain ; Amassian, Aram ; Del Gobbo, Silvano
    Chemical bath deposition (CBD) of tin oxide (SnO2) thin films as an electron-transport layer (ETL) in a planar-heterojunction n-i-p organohalide lead perovskite and organic bulk-heterojunction (BHJ) solar cells is reported. The amorphous SnO2 (a-SnO2) films are grown from a nontoxic aqueous bath of tin chloride at a very low temperature (55 °C) and do not require postannealing treatment to work very effectively as an ETL in a planar-heterojunction n-i-p organohalide lead perovskite or organic BHJ solar cells, in lieu of the commonly used ETL materials titanium oxide (TiO2) and zinc oxide (ZnO), respectively. Ultraviolet photoelectron spectroscopy measurements on the glass/indium-tin oxide (ITO)/SnO2/methylammonium lead iodide (MAPbI3)/2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene device stack indicate that extraction of photogenerated electrons is facilitated by a perfect alignment of the conduction bands at the SnO2/MAPbI3 interface, while the deep valence band of SnO2 ensures strong hole-blocking properties. Despite exhibiting very low electron mobility, the excellent interfacial energetics combined with high transparency (Egap,optical > 4 eV) and uniform substrate coverage make the a-SnO2 ETL prepared by CBD an excellent candidate for the potentially low-cost and large-scale fabrication of organohalide lead perovskite and organic photovoltaics.
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    Optoelectronic and photovoltaic properties of the air-stable organohalide semiconductor (CH < inf > 3 < /inf > NH < inf > 3 < /inf > ) < inf > 3 < /inf > Bi < inf > 2 < /inf > I < inf > 9 < /inf >
    ( 2016-01-01) Abulikemu, Mutalifu ; Ould-Chikh, Samy ; Miao, Xiaohe ; Alarousu, Erkki ; Murali, Banavoth ; Ngongang Ndjawa, Guy Olivier ; Barbé, Jérémy ; El Labban, Abdulrahman ; Amassian, Aram ; Del Gobbo, Silvano
    Lead halide perovskite materials have shown excellent optoelectronic as well as photovoltaic properties. However, the presence of lead and the chemical instability relegate lead halide perovskites to research applications only. Here, we investigate an emerging lead-free and air stable compound (CH3NH3)3Bi2I9 as a non-toxic potential alternative to lead halide perovskites. We have synthesized thin films, powders and millimeter-scale single crystals of (CH3NH3)3Bi2I9 and investigated their structural and optoelectronic properties. We demonstrate that the degree of crystallinity strongly affects the optoelectronic properties of the material, resulting in significantly different band gaps in polycrystalline thin films and single crystals. Surface photovoltage spectroscopy reveals outstanding photocharge generation in the visible ( < 700 nm) region, while transient absorption spectroscopy and space charge limited current measurements point to a long exciton lifetime and a high carrier mobility, respectively, similar to lead halide perovskites pointing to the remarkable potential of this semiconductor. Photovoltaic devices fabricated using this material yield a low power conversion efficiency (PCE) to date, but the PCE is expected to increase with improvements in thin film processing and device engineering.