Sharif Digital Repository

We report a study on chalcopyrite solar cells fabricated by low-cost, nonvacuum, and selenization-free methods. Superstrate-type CuInS2 (CIS) thin-film solar cells were prepared by sequential ink deposition. The CIS film was formed from a stable low-carbon ink, which was synthesized at low temperature (<120 °C). The CIS nanoparticle ink was prepared with n-butylamine and acetic acid as the solvent and stabilizer, respectively. The viscous and stable ink that formed through the dispersion of the final nanoparticles in N,N-dimethylformamide (DMF) could be deposited readily onto the substrate. The major features of the obtained ink are the small amount of impurity phases and negligible carbon... 

A solution-processed, bottom-up nanowire network electrode is developed and employed in a bulk heterojunction colloidal quantum dot solar cell. The electrode features a ZnO template which is converted into locally connected, infi ltratable TiO2 nanowires. The new electrode allows the application of a thicker light absorbing fi lm without compromising the charge extraction, as reported by Edward H. Sargent, Ghassan Jabbour, and co-workers on page 1769. The frontispiece shows schematically the electrode shape and the resultant device architecture  

Herein, a solution-processed, bottom-up-fabricated, nanowire network electrode is developed. This electrode features a ZnO template which is converted into locally connected, infiltratable, TiO2 nanowires. This new electrode is used to build a depleted bulk heterojunction solar cell employing hybrid-passivated colloidal quantum dots. The new electrode allows the application of a thicker, and thus more light-absorbing, colloidal quantum dot active layer, from which charge extraction of an efficiency comparable to that obtained from a thinner, planar device could be obtained  

Planar superstrate CuInS2 (CIS) solar cell devices are fabricated using totally solution-processed deposition methods. These Cd-free devices are structured by FTO/TiO2/In2S3/CIS/carbon, where TiO2 and In2S3 are deposited by spray pyrolysis, and a CIS film is deposited using spin-coating followed by annealing at 250 °C. The pasted carbon layer is utilized as the anode. No further sulfurization or selenization is employed. The Cu/In ratio in the ink is found as a critical factor affecting the morphology and crystallinity of the film as well as the photovoltaic performance of the device. An optimum Cu/In = 1.05 results in large-grain films with sharp diffraction peaks and, subsequently, optimal... 

Solution processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) are promising materials for potential optoelectronic applications. To date, efficiency of the excitation energy transfer into GO and RGO thin layers has not been investigated in terms of donor-acceptor separation distance. In the present work, we study nonradiative energy transfer (NRET) from CdSe/CdS quantum dots into single and/or double layer GO or RGO using time-resolved fluorescence spectroscopy. We observe shorter lifetimes as the separation distance between the QDs and GO or RGO decreases. In accordance with these lifetimes, the rates reveal the presence of two different mechanisms... 

Brake friction materials filled with nanoalumina were produced by both conventional and solvent-assisted mixing methods. It was shown that nanoalumina loading led to the reduction of friction coefficient and improvement in mechanical, wear and thermal behaviors. Such behavior was attributed to the role of nanoalumina in producing stable friction layer and easy conduction path in matrix. It was postulated that nanoalumina is able to attach on the surface of microalumina facilitating the rolling of microalumina at interface. Solution-processed samples exhibited lower improvement in tribological and mechanical properties compared to the conventional mixing due to the limited interaction between... 

In the literature, although a few studies can be found regarding the application of revenue management to special cases of Make-to-Order manufacturing systems with stochastic capacity, there is not any study when capacity or demand (or both) are random variables with general distribution function. Therefore, in this paper, an approach is developed to study a more general case of Make-to-Order manufacturing systems based on the concept of revenue management. Due to the random nature of capacity and demand, the exact size of capacity to satisfy the orders is not known at the time of arriving orders. Consequently, the vital decision is either to accept or reject an order at the time of arrival.... 

Perovskite solar cells have been constructed under the standard procedure by employing soluble tetratriphenylamine-substituted Zn phthalocyanine as hole transporting material. Solution processed device construction was carried out under ambient conditions of 50–60% ambient humidity. Triphenylamine substitution played the double role of imparting solubility to the core metal phthalocyanine as well as to introduce electron-rich ligands, which could enhance the role of Zn phthalocyanine as hole transporter. Indeed, the obtained material was functional. The present data highlight tetratriphenylamine-substituted Zn phthalocyanine as hole transporting material but also highlight the importance of... 

Copper phthalocyanine can effectively act as alternative small molecule hole transporting material in perovskite solar cells. In order to produce solution processed devices, a soluble copper phtalocyanine has been synthesized by n-butyl substitution and it was compared to commercially available tert-butyl substituted copper phthalocyanine. It was found that the configuration of the butyl chain plays a very important role in film conductivity and in the subsequent efficiency of solar cells, n-bytyl derivative being the most effective hole transporter. Such a result is due to the fact that n-butyl derivative allows better packing of the molecules in the film and stronger π-π interaction  

This paper attempts to develop the optimal solution for an inventoryproblem consisting of a single machine which produces items some of which may bedefective. We assume that no shortages are allowed and all defective items areto be reworked. Setup cost for rework and waiting time of defectives areconsidered. We consider two different policies where in the first policy in eachcycle after the regular production the machine is setup for the rework ofdefectives of the same cycle. In the second policy several cycles constitute aperiod. All the defectives produced in the period are reworked in the last cycleof that period. At the end of the rework cycle the whole process starts allover again. One... 

The antisolvent method has been used extensively to induce the growth of high-quality perovskite layers for efficient solar cells. However, uncontrollable nucleation and crystallization increases the risk of formation of undesirable defects. Here, we report a facile way to control the nucleation and crystallization stages in perovskite formation by changing the temperature of chlorobenzene (CB) in the antisolvent method. When CB is injected on the spinning substrate with a precursor solution, CB temperature affects the nucleation process as well as the crystallization process. As the CB temperature increases, nuclei increase in size, leading to the formation of larger perovskite crystals... 

Fullerene derivatives with a strong electron-accepting ability play a crucial role in enhancing both the performance and stability of perovskite solar cells (PSCs). However, most of the used fullerene molecules are based on [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which limits the device performance due to difficulties in preparing high-quality and uniform thin films. Herein, solution-processable azahomofullerene (AHF) derivatives (abbreviated as AHF-1 and AHF-2) are reported as novel and effective electron-transport layers (ETLs) in p-i-n planar PSCs. Compared to the control PCBM ETL-based PSCs, the devices based on AHFs exhibit higher photovoltaic performances, which is... 

In the last decade, the power conversion efficiency (PCE) of solution-processed perovskite solar cells (PSCs) in the lab-scale has reached an incredible level of 25.5%. Generally, PSCs are composed of a stack consisting of a perovskite thin-film sandwiched between an electron transporting layer (ETL) and a hole transporting layer (HTL). Although the quality of the ETL and HTL interfaces with the perovskite thin-film is important, the quality of the perovskite thin-film is also critical to achieving high-performance PSCs. Low-temperature deposition of organic-inorganic perovskite thin-films by simple solution processes is one of the significant advantages of PSCs compared to other... 

This paper addresses the feasibility of applying realtime steganalysis to the Internet data. To reach a practical solution, we have employed offline procedures to minimize the volume of the data to be processed by an online real-time system. Possible offline services that can be provided to an online system then led us to appropriate network designs for the online system. To go into detail of the online systems, we have carefully analyzed some well-known, state-of-the-art steganalysis algorithms and estimated their processing power and memory requirements. Some formulas are derived to relate the network bit rate with the number of the processing units, their processing power, and memory... 

Today manufacturing of high efficiency chalcogenide thin film solar cells is based on high cost vacuum-based deposition processes at high temperature (>500 °C) and in chalcogen -containing atmosphere. In this paper, we introduce a simple vacuum-free and selenization-free, solution processing for fabricating a superstrate-type CuInS2 (CIS) solar cell. The absorber, buffer and blocking layers were all deposited by spin coating of molecular precursor inks. We demonstrate the deposition of In2S3 buffer layer by sol-gel spin casting for the first time. The rapid sintering process of CIS layer was carried out at 250 °C that is considered a very low temperature in CIGS thin-film technologies. A... 

The fabrication of high performance, solution-processed CIGS family solar cells is based on high-temperature crystallization processes in chalcogen-containing atmosphere and/or using dangerous solvents like hydrazine. The non-hydrazine sulfurization- and selenization-free reports typically suffer from poor grain structures. We report a facile strategy to overcome grain growth limitations at very low temperature processing (250 °C). Selenium free Superstrate configuration CuInS2 (CIS) solar cells are fabricated using a nanocrystals ink which avoiding from high temperature selenization or/and sulfurization is targeted. We investigated the effect of intentional M doping (M = Sb, Zn, Cd and Sn)... 

In terms of manufacturability, there is a high tendency to deposit light-absorbing CuInS2 films by solution processing methods like ink-based depositions. In particular, for nanoparticle inks, the synthesis of highly dispersed and stable inks, with uniformity in the deposition process, is a serious challenge. Here, we demonstrate a novel two-step low-temperature CuInS2 film deposition method in which the In2S3 is deposited first. It then partially is converted into CuInS2 through the infiltration of Cu+ ions in the In2S3 layer in a dip-coating process. The resulting films are highly uniform, with diffraction peaks indicating the formation of pure CuInS2 phase. The proper stoichiometry of... 

Transition metal oxides are being more frequently used as hole injection layer (HIL) in organic light emitting diodes (OLEDs), in place of polymer HILs such as PEDOT:PSS. The very thin films of the metal oxide HILs are usually deposited using vapor deposition, in order to create uniform films. Here, we report OLEDs fabricated using solution processed MoOx films as the HIL and super yellow as the emissive layer. The performance of the devices is comparable to PEDOT:PSS based devices, while the stability tests show the lifetime of MoOx-based devices is 4 × 106 h, about 40 times longer than PEDOT:PSS devices, at typical working condition. X-ray photoelectron spectroscopy (XPS) indicates both...