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    Photovoltaic parameters and stability study of HTM-free mixed-cation perovskite solar cells by incorporating additives to absorbing layers

    , Article Journal of Materials Science: Materials in Electronics ; Volume 31, Issue 9 , 2020 , Pages 7123-7132 Doosthosseini, F ; Behjat, A ; Karimi Zarchi, A ; Taghavinia, N ; Mirjalili, B. F ; Sharif University of Technology
    Springer  2020
    In this study, quick route-coating is practiced to substitute methyl ammonium (MA) cation with formamidinium (FA) at different ratios. Through optimizing the MA:FA ratio, a maximum power conversion efficiency (PCE) of 8.31% is achieved for holes transporting material-free MA0.8FA0.2PbI3 mixed PSCs with the JSC of 19.02 mA/cm2, VOC of 0.859 V and FF of 50.88%. Then, to improve the performance, stability and carrier transport dynamic, various additives (PVA, PVP, PEG and EC) are incorporated into the perovskite layer. The treatment of perovskites with additives has proved to cause significant changes in the surface roughness, charge accumulation, charge transport, charge transport resistance,... 

    Investigation the Effect of Formamidinium Lead Halide on the Stability and Performance of Graphene Phototransistors Based on Lead Sulfide

    , Ph.D. Dissertation Sharif University of Technology Aynehband, Samaneh (Author) ; Simchi, Abdolreza (Supervisor)
    Enhancing the detection range, sensitivity and stability of phototdetectors due to their vast applications are in great importance. In recent years, Lead sulfide quantum dots, in order to their absorption over a wide range of wavelengths including Near-infrared (NIR), multiple exciton generation effect and solution processability are promising materials.However, long organic surface ligands which are necessary in synthesis process can suppress the carrie transport and the common method to overcome this weakness, is ligand exchange process. In this way, using short organic ligands because of their low electron mobility and methylammonium lead iodide ligands in order to their instability,... 

    Incorporation of CsPbI3 Perovskite Quantum Dots as Interrfacial Layer for Highly Efficient Cs0.05MA0.95PbI3 Perovskite Solar Cells

    , M.Sc. Thesis Sharif University of Technology Kamraninejad, Vahid (Author) ; Simchi, Abdolreza (Supervisor)
    Despite the excellent photovoltaic performance of perovskite solar cells (PSCs), the instability of PSCs under severe environment (e.g., humidity, intense light) limits further commercialization of such devices. Therefore, in recent years, many researches are conducted on utilizing Perovskite Quantum Dots (PQDs) to enhance performance of PSCs. Herein, CsPbI3 PQDs interfacial layer is incorporated in the perovskite/hole transport material (HTM) interface, on the purpose of increasing charge carrier mobility and preventing electron-hole recombination to increase performance of the PSCs. CsPbI3 PQDs is synthesized at 170℃ with oleic acid and oleylamine as organic ligands by hot-injection... 

    Interface engineering of perovskite solar cell using a reduced-graphene scaffold

    , Article Journal of Physical Chemistry C ; Volume 120, Issue 35 , Volume 120, Issue 35 , 2016 , Pages 19531-19536 ; 19327447 (ISSN) Tavakoli, M. M ; Tavakoli, R ; Hasanzadeh, S ; Mirfasih, M. H ; Sharif University of Technology
    American Chemical Society 
    Interface engineering of solar cell device is a prominent strategy to improve the device performance. Herein, we synthesize reduced-graphene scaffold (rGS) by using a new and simple chemical approach. In this regard, we synthesize a hollow structure of graphene and then fabricate a three-dimensional scaffold of graphene with a superior surface area using electrophoretic process. We employ this scaffold as an interface layer between the electron transfer and absorber layers in perovskite solar cell. The characterization tests and photovoltaic results show that rGS improves the carrier transportation, yielding a 27% improvement in device performance as compared to conventional device. Finally,... 

    Trap density measurement in three-dimensional nanostructured photoelectrode of titanium dioxide with various morphologies

    , Article Applied Physics A: Materials Science and Processing ; Volume 122, Issue 4 , 2016 ; 09478396 (ISSN) Sasanpour, P ; Mohammadpour, R ; Sharif University of Technology
    Springer Verlag  2016
    Three-dimensional TiO2 nanostructures take advantages of large surface area and superior light-harvesting efficiency, as well as appropriate charge carrier transport and separation features. Here in this research, we report for the first time on measurement of density of localized trap states in three-dimensional TiO2 nanostructures with various morphologies. Bare 1-dimensional TiO2 nanofibers have been synthesized via two different methods: electrospinning and hydrothermal processes. The surface of TiO2 nanofibrous has been modified with nanoparticles and nanobranches thorough second hydrothermal process. Various morphologies of nanostructured TiO2 have been fabricated including... 

    Perovskite/hole transport layer interface improvement by solvent engineering of spiro-ometad precursor solution

    , Article ACS Applied Materials and Interfaces ; Volume 11, Issue 47 , 2019 , Pages 44802-44810 ; 19448244 (ISSN) Taherianfard, H ; Kim, G. W ; Ebadi, F ; Abzieher, T ; Choi, K ; Paetzold, U. W ; Richards, B. S ; Alrhman Eliwi, A ; Tajabadi, F ; Taghavinia, N ; Malekshahi Byranvand, M ; Sharif University of Technology
    American Chemical Society  2019
    Perovskite solar cells (PSCs) are one of the most promising emerging energy-conversion technologies because of their high power conversion efficiencies (PCEs) and potentially low fabrication cost. To improve PCE, it is necessary to develop PSCs with good interfacial engineering to reduce the trap states and carrier transport barriers present at the various interfaces of the PSCs' architecture. This work reports a facile method to improve the interface between the perovskite absorber layer and the hole transport layer (HTL) by adding a small amount of acetonitrile (ACN) in the Spiro-OMeTAD precursor solution. This small amount of ACN dissolves the surface of the perovskite layer, allowing the... 

    Surface treatment of perovskite layer with guanidinium iodide leads to enhanced moisture stability and improved efficiency of perovskite solar cells

    , Article Advanced Materials Interfaces ; Volume 7, Issue 14 , 2020 Chavan, R. D ; Prochowicz, D ; Tavakoli, M. M ; Yadav, P ; Hong, C. K ; Sharif University of Technology
    Wiley-VCH Verlag  2020
    Interfacial engineering between the perovskite and hole transport layers has emerged as an effective way to improve perovskite solar cell (PSC) performance. A variety of organic halide salts are developed to passivate the traps and enhance the charge carrier transport. Here, the use of guanidinium iodide (GuaI) for interfacial modification of mixed-cation (Cs)x(FA)1−xPbI3 perovskite films, which results in the formation of a low-dimensional δ-FAPbI3-like phase on the 3D perovskite surface, is reported. The presence of this thin layer facilitates charge transfer at interfaces and reduces charge carrier recombination pathways as evidenced by enhanced carrier lifetimes and favorable interfacial... 

    Electrically charged Andreev modes in two-dimensional tilted Dirac cone systems

    , Article Physical Review B ; Volume 101, Issue 21 , 2020 Faraei, Z ; Jafari, S. A ; Sharif University of Technology
    American Physical Society  2020
    In a graphene-based Josephson junction, the Andreev reflection can become specular, which gives rise to propagating Andreev modes. These propagating Andreev modes are essentially charge neutral and therefore they transfer energy but not electric charge. One main result of this work is that when the Dirac theory of graphene is deformed into a tilted Dirac cone, the breaking of charge conjugation symmetry of the Dirac equation renders the resulting Andreev modes electrically charged. We calculate an otherwise zero charge conductance arising solely from the tilt parameters ζâ -=(ζx,ζy). The distinguishing feature of such a form of charge transport from the charge transport caused by normal... 

    Biphasic TiO2 nanoleafed nanorod electrode for dye-sensitized solar cell

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 123 , 2020 Daneshvar e Asl, S ; Sadrnezhaad, S. K ; Sharif University of Technology
    Elsevier B.V  2020
    The thin-film of hierarchical rutile/anatase TiO2 nanorod/nanoleafs on fluorine-doped tin oxide glass was prepared via a facile method. For this purpose, the hydrothermal method was used for the synthesis of rutile-phase nanorods on the TiO2 seeded FTO, and aqueous chemistry was applied for growing anatase-phase nanoleafs on the nanorods. The structural, morphological, and optical properties of coating characterized, and the thin-film utilized as the photoelectrode for dye-sensitized solar cell. The energy conversion efficiency of the newly developed nanostructure was higher than that of TiO2 nanorod thin-film by 40%. This increase could be ascribed to: (1) superior specific surface area...