Sharif Digital Repository

Solution-processed quantum dots (QDs) have attracted significant attention for the low-cost fabrication of optoelectronic devices. Here, we synthesized PbS QDs via hot injection method and passivated the trap states by using short thiols and dopant elements for photovoltaic application. In order to study the effect of dopants on photovoltaic application, PbS QDs were doped by using three different cations: Cadmium, Calcium, and Zinc. We utilized Time resolvel Photoluminescence measurement to study the carriers lifetime for different samples and found that the carriers life time increases ∼80% by using Cd as a dopant compared with undoped sample. In addition, the results of J-V measurement... 

Lead sulfide quantum dots (PbS QDs) were decorated onto a graphene surface in a semi-core-shell structure using supercritical ethanol. The temperature of ethanol played significant role in controlling size and agglomeration of QDs as well as the extent of reduction of graphene. Average size of the QDs was estimated by transmission electron microscopy to be around 3.96 nm and by quantum models to be about 4.34 nm. PbS QDs prepared at 330 °C were of high purity, and the yield was 99%. Instrumental and chemical analyses demonstrated formation of a strong bond between PbS QDs and graphene, through a Pb-O-C bridge. UV and photoluminescence measurements along with theoretical considerations... 

Herein, a simple and novel method was used to synthesize a new structure of graphene which can be called hollow graphene. First, the ZnO-Graphene QDs synthesized by solution method and then ZnO QDs were dissolved from this structure using an acidic solution to obtain hollow structure of graphene. Afterward, this structure was used in PbS QDs solar cell in order to improve the transport of electron and decrease the recombination of the carriers. A power conversion efficiency of 5.3% was obtained using hollow graphene as a fast electron extraction layer due to the enhancement of EQE and current density. The improvement of PCE in this device was corresponded to efficient photosensitized... 

Nanowire arrays of copper oxide were first grown vertically using simple and cost effective thermal oxidation method on a copper foil. Subsequently, in order to deposit and grow PbS nanocyrstalline thin films on CuO NWs by utilizing the chemical bath deposition technique, these arrays were immersed as the substrate in the reaction solution consisting of Pb(NO3)2, (NH2)2CS and NaOH. The final products were characterized in detail by which the formation of uniform, unique arrays of CuO@PbS core–shell NWs was confirmed. Due to the nature of methods employed in synthesis of this hetero structure, the tuning of core and shell size and consequently properties of the novel structure is easily... 

PbS nanoparticles were in situ deposited on graphene sheets by a successive ionic liquid adsorption and reaction method to prepare a graphene/PbS composite counter electrode for CdS/CdSe quantum dot sensitized solar cells (QDSCs). Under 1 sun illumination, the cells with graphene/PbS counter electrodes (CEs) show a maximum energy conversion efficiency of 2.63%, which is remarkably higher than that of those employing PbS (1.28%) or graphene (0.23%) CEs. Electrochemical impedance spectroscopy analysis shows that graphene/PbS composite counter electrodes have lower charge-transfer resistance at the interface of the CE and the polysulfide redox electrolyte, compared to those cells with PbS and... 

The type of passivating ligands and the ligand exchange method influence the quality of lead sulfide quantum dot films. This imparts on the efficiency of optoelectronic devices. To get a compact arrangement of the nanocrystals in a thin film (⁓100 nm) via self-assembling, we used organic-inorganic perovskites with mixed halides for the solid-state exchange of oleic acid ligands on PbS QDs (⁓ 4 nm). Formamidinium lead halides FAPbIxBr3-x (x= 3,2,1,0) were used. X-ray spectroscopy shows that successful replacement of oleic acid with FA happens by short immersion of the films (2 min) in the solution. Transmission electron microscopy shows that nano-scale cracks, short-range ordering, and fusion...