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    AuthorBakr, Osman (5)
    Mohammed, Omar F. (5)
    Banavoth, Murali (4)Parida, Manas R. (3)Abdelhady, Ahmed L. (2)View MoreDepartment
    Chemical Science Program (5)
    KAUST Catalysis Center (KCC) (5)
    KAUST Solar Center (KSC) (5)
    Materials Science and Engineering Program (5)Physical Sciences and Engineering (PSE) Division (5)View MoreJournalThe Journal of Physical Chemistry Letters (3)Inorganic Chemistry (1)Journal of the American Chemical Society (1)KAUST Grant NumberURF/1/1373-01-01 (1)URF/1/1741-01-01 (1)URF/1/2268-01-01 (1)Publisher
    American Chemical Society (ACS) (5)
    Type
    Article (5)
    Year (Issue Date)
    2016 (5)
    Item Availability
    Metadata Only (5)

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    Temperature-Induced Lattice Relaxation of Perovskite Crystal Enhances Optoelectronic Properties and Solar Cell Performance

    Banavoth, Murali; Yengel, Emre; Peng, Wei; Chen, Zhijie; Alias, Mohd Sharizal; Alarousu, Erkki; Ooi, Boon S.; Burlakov, Victor; Goriely, Alain; Eddaoudi, Mohamed; Bakr, Osman; Mohammed, Omar F. (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2016-12-16) [Article]
    Hybrid organic-inorganic perovskite crystals have recently become one of the most important classes of photoactive materials in the solar cell and optoelectronic communities. Albeit improvements have focused on state-of-the-art technology including various fabrication methods, device architectures, and surface passivation, progress is yet to be made in understanding the actual operational temperature on the electronic properties and the device performances. Therefore, the substantial effect of temperature on the optoelectronic properties, charge separation, charge recombination dynamics, and photoconversion efficiency are explored. The results clearly demonstrated a significant enhancement in the carrier mobility, photocurrent, charge carrier lifetime, and solar cell performance in the 60 ± 5 °C temperature range. In this temperature range, perovskite crystal exhibits a highly symmetrical relaxed cubic structure with well-aligned domains that are perpendicular to a principal axis, thereby remarkably improving the device operation. This finding provides a new key variable component and paves the way toward using perovskite crystals in highly efficient photovoltaic cells.
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    Engineering Interfacial Charge Transfer in CsPbBr3 Perovskite Nanocrystals by Heterovalent Doping

    Begum, Raihana; Parida, Manas R.; Abdelhady, Ahmed L.; Banavoth, Murali; AlYami, Noktan Mohammed; Ahmed, Ghada H.; Hedhili, Mohamed N.; Bakr, Osman; Mohammed, Omar F. (Journal of the American Chemical Society, American Chemical Society (ACS), 2016-12-30) [Article]
    Since compelling device efficiencies of perovskite solar cells have been achieved, investigative efforts have turned to understand other key challenges in these systems, such as engineering interfacial energy-level alignment and charge transfer (CT). However, these types of studies on perovskite thin-film devices are impeded by the morphological and compositional heterogeneity of the films and their ill-defined surfaces. Here, we use well-defined ligand-protected perovskite nanocrystals (NCs) as model systems to elucidate the role of heterovalent doping on charge-carrier dynamics and energy level alignment at the interface of perovskite NCs with molecular acceptors. More specifically, we develop an in situ doping approach for colloidal CsPbBr3 perovskite NCs with heterovalent Bi3+ ions by hot injection to precisely tune their band structure and excited-state dynamics. This synthetic method allowed us to map the impact of doping on CT from the NCs to different molecular acceptors. Using time-resolved spectroscopy with broadband capability, we clearly demonstrate that CT at the interface of NCs can be tuned and promoted by metal ion doping. We found that doping increases the energy difference between states of the molecular acceptor and the donor moieties, subsequently facilitating the interfacial CT process. This work highlights the key variable components not only for promoting interfacial CT in perovskites, but also for establishing a higher degree of precision and control over the surface and the interface of perovskite molecular acceptors.
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    pH-Induced Surface Modification of Atomically Precise Silver Nanoclusters: An Approach for Tunable Optical and Electronic Properties

    AbdulHalim, Lina G.; Hooshmand, Zahra; Parida, Manas R.; Aly, Shawkat Mohammede; Le, Duy; Zhang, Xin; Rahman, Talat S.; Pelton, Matthew; Losovyj, Yaroslav; Dowben, Peter A.; Bakr, Osman; Mohammed, Omar F.; Katsiev, Khabiboulakh (Inorganic Chemistry, American Chemical Society (ACS), 2016-10-24) [Article]
    Noble metal nanoclusters (NCs) play a pivotal role in bridging the gap between molecules and quantum dots. Fundamental understanding of the evolution of the structural, optical, and electronic properties of these materials in various environments is of paramount importance for many applications. Using state-of-the-art spectroscopy, we provide the first decisive experimental evidence that the structural, electronic, and optical properties of Ag-44(MNBA)(30) NCs can now be tailored by controlling the chemical environment. Infrared and photoelectron spectroscopies clearly indicate that there is a dimerization between two adjacent ligands capping the NCs that takes place upon lowering the pH from 13 to 7.
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    Shape-Tunable Charge Carrier Dynamics at the Interfaces between Perovskite Nanocrystals and Molecular Acceptors

    Ahmed, Ghada H.; Liu, Jiakai; Parida, Manas R.; Banavoth, Murali; Bose, Riya; AlYami, Noktan Mohammed; Hedhili, Mohamed N.; Peng, Wei; Pan, Jun; Besong, Tabot M.D.; Bakr, Osman; Mohammed, Omar F. (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2016-09-22) [Article]
    Hybrid organic/inorganic perovskites have recently emerged as an important class of materials and have exhibited remarkable performance in photovoltaics. To further improve their device efficiency, an insightful understanding of the interfacial charge transfer (CT) process is required. Here, we report the first direct experimental observation of the tremendous effect that the shape of perovskite nanocrystals (NCs) has on interfacial CT in the presence of a molecular acceptor. A dramatic change in CT dynamics at the interfaces of three different NC shapes, spheres, platelets, and cubes, is recorded. Our results clearly demonstrate that the mechanism of CT is significantly affected by the NC shape. More importantly, the results demonstrate that complexation on the NC surface acts as an additional driving force not only to tune the CT dynamics but also to control the reaction mechanism at the interface. This observation opens a new venue for further developing perovskite NCs-based applications.
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    Heterovalent Dopant Incorporation for Bandgap and Type Engineering of Perovskite Crystals

    Abdelhady, Ahmed L.; Saidaminov, Makhsud I.; Banavoth, Murali; Adinolfi, Valerio; Voznyy, Oleksandr; Katsiev, Khabiboulakh; Alarousu, Erkki; Comin, Riccardo; Dursun, Ibrahim; Sinatra, Lutfan; Sargent, Edward H.; Mohammed, Omar F.; Bakr, Osman (The Journal of Physical Chemistry Letters, American Chemical Society (ACS), 2016-01-07) [Article]
    Controllable doping of semiconductors is a fundamental technological requirement for electronic and optoelectronic devices. As intrinsic semiconductors, hybrid perovskites have so far been a phenomenal success in photovoltaics. The inability to dope these materials heterovalently (or aliovalently) has greatly limited their wider utilizations in electronics. Here we show an efficient in situ chemical route that achieves the controlled incorporation of trivalent cations (Bi3+, Au3+, or In3+) by exploiting the retrograde solubility behavior of perovskites. We term the new method dopant incorporation in the retrograde regime. We achieve Bi3+ incorporation that leads to bandgap tuning (∼300 meV), 104 fold enhancement in electrical conductivity, and a change in the sign of majority charge carriers from positive to negative. This work demonstrates the successful incorporation of dopants into perovskite crystals while preserving the host lattice structure, opening new avenues to tailor the electronic and optoelectronic properties of this rapidly emerging class of solution-processed semiconductors. © 2016 American Chemical Society.
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