Sharif Digital Repository

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,... 

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,... 

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 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... 

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... 

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... 

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...