Sharif Digital Repository

Interfacial studies and band alignment engineering on the electron transport layer (ETL) play a key role for fabrication of high-performance perovskite solar cells (PSCs). Here, an amorphous layer of SnO2 (a-SnO2) between the TiO2 ETL and the perovskite absorber is inserted and the charge transport properties of the device are studied. The double-layer structure of TiO2 compact layer (c-TiO2) and a-SnO2 ETL leads to modification of interface energetics, resulting in improved charge collection and decreased carrier recombination in PSCs. The optimized device based on a-SnO2/c-TiO2 ETL shows a maximum power conversion efficiency (PCE) of 21.4% as compared to 19.33% for c-TiO2 based device.... 

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... 

Parameter extraction of the five-parameter single-diode model of solar cells and modules from experimental data is a challenging problem. These parameters are evaluated from a set of nonlinear equations that cannot be solved analytically. On the other hand, a numerical solution of such equations needs a suitable initial guess to converge to a solution. This paper presents a new set of approximate analytical solutions for the parameters of a five-parameter single-diode model of photovoltaic (PV) cells and modules. The proposed solutions provide a good initial point which guarantees numerical analysis convergence. The proposed technique needs only a few data from the PV current-voltage... 

The corrosion inhibition effect of zinc acetylacetonate (ZAA) and benzothiazole (BTH) mixture was evaluated for mild steel in 3.5% NaCl solution. To this end, ZAA:BTH mixtures ranged from 6:1 to 1:6 mol ratios were examined by weight loss and open circuit potential to obtain optimal mole ratio. The optimal mixture of ZAA:BTH at 1:5 mol ratio showed a significant corrosion inhibition efficiency proved by electrochemical impedance spectroscopy and polarization studies. The addition of the optimal mixture of ZAA:BTH to epoxy coating showed a considerable increase of corrosion protection evaluated by salt spray exposure  

Three new chromophores based on the triphenylamine (MM, DM, DN) with various novel electron withdrawing anchoring groups have been synthesized for use in dye-sensitized solar cells (DSSCs). The sensitizers were characterized by 1H and 13C NMR, Mass, UV–Vis, and electrochemical analysis. The HOMO and LUMO electron distributions of the sensitizers were calculated using density functional theory on a B3LYP level for geometry optimization. The DSSC device based on DM dye showed the best photovoltaic performance among MM and DN dyes: maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 98 %, short circuit current (JSC) of 4.58 mA/cm2, open circuit voltage (VOC) of... 

In the current investigation, four novel donoracceptor type organic dyes including (DPA-Ba, DPA-Hy, DPA-Rh, DPA-Cy), are proposed and their photophysical and electrochemical properties as well as dye-sensitized solar cell performance are systematically investigated. Among these dyes diphenylamine is utilized as an-electron donor while barbituric acid, hydantoin, rhodanine-n-acetic acid and cyano acetic acid, are proposed as anchoring groups as dye-sensitized solar cells (DSSCs). The synthesized dyes are characterized using FT-IR, NMR, mass spectrometry, absorbance and electrochemical measurements. The photophysical, electrochemical and photovoltaic properties of the solar cells based on... 

Carbon nanotubes (CNT) have unique electronic properties and remarkable optical properties. Despite of on layer thickness of CNTs, it has able to absorb photons from visible to far infrared and terahertz. These unique properties lets to create heterojunction devices by semiconductor/CNTs or metal/CNTs junctions e.g. photodiodes, sensor and heterojunction solar cell. The CNTs can play the role of a heterojunction component for charge separation as a high conductive network for charge transport and as a transparent electrode for light illumination and charge collection. The main objective of the present article is to establish a relation between interface recombination and the characteristics... 

Organic-inorganic halide perovskite solar cells have attracted considerable interest due to their high efficiency and low fabrication cost. Au and Ag are usually used as the back contact metals but have limitations such as Au is too expensive and Ag is unstable. Here, Pt, Au, Ni, Cu, Cr and Ag were studied as the back contact electrodes for perovskite solar cells. We looked at how the work function of metals can affect their photovoltaic characteristics. The compositional and electrical characterizations were studied using X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The general trend observed was that the shunt resistance and open-circuit voltage... 

The conventional solar cell architectures include a p-n junction of c-Si sandwiched by rear and front contacts. The conventional approach features a complex as well as expensive procedure. Here, we propose a new architecture for p-n heterojunction solar cells prepared by a simple and cost-effective procedure. In this regard, (1) a silicon wafer underwent surface treatment through electrochemical anodization. To prepare a stick junction, (2) photoactive TiO2 nanoparticles were deposited over the porous layer by electrophoretic technique. Finally, (3) indium tin oxide (ITO) was sputtered. During the fabrication steps, we examined various anodization times ranging from 6 to 12 min to study the... 

Perovskite solar cells suffer from various instabilities on all time scales. Some of them are driven by light, in particular when employing compounds with mixed halides. Such light soaking effects have been observed to result in performance changes of solar-cell devices. They have also been spectroscopically investigated in detail on films, where the formation of a low-gap iodine-rich phase, seen as a red shift of the PL, has been found to be responsible for a reduced open-circuit voltage. However, studies synchronously examining device performance and its relation to spectroscopy data are scarce. Here, we perform an in operando study, where we investigate the changes of open-circuit voltage... 

This paper reports on the synthesis of ZnO nanowires (NWs), as well asthe compound nanostructures of nanoparticles (NPs) and nanowires (NWs+NPs) with different coating layers of NPs on the top of NWs and their integration in dye-sensitized solar cells (DSSCs). In compound nanostructures, NWs offer direct electrical pathways for fast electron transfer, and the NPs of ZnOdispread and fill the interstices between the NWs of ZnO, offering a huge surface area for enough dye anchoring and promoting light harvesting. A significant photocurrent density of 2.64mA/cm2 and energy conversion efficiency of 1.43% was obtained with NWs-based DSSCs. The total solar-to-electric energy conversion efficiency... 

TiO2 nanotubes were synthesized using a modified autoclave-free thermal method from as-prepared initial powders. The size of initial powders (IP) was found to be critical in determining the morphology and crystal structure of the final product. Oleylamine (OA) was used as the polymer agent in the preparation of initial powders with different mol ratios of OA/Ti: 1, 5, and 10. X-ray diffraction analysis depicted that the increase of mole ratio up to 10 resulted in smaller nanoparticles with the sizes of about 8 nm. It was also deliberated that low temperature thermally treated IP showed the characteristic diffraction pattern of titanate phase of nanotubes. Scanning electron... 

Interleaved DC-DC boost converters are interesting choices in applications like fuel cells and photovoltaic systems. Although this converter offers low current ripple, but an open-circuit switch fault can lead to unacceptable current ripples. In this paper, a very fast and simple method is proposed to detect an open-circuit switch fault and its location. This method doesn't need any additional sensors, is efficient in CCM and DCM modes of operation, and can detect the fault in less than one switching period. Moreover, this method is suitable for implementation on an FPGA, due to the use of simple math and state machine blocks. Simulations are carried out to validate the effectiveness of this... 

In this paper, a fast and practical method is proposed for open-circuit (OC) fault diagnosis (FD) in a three-phase quasi-Z-source inverter (q-ZSI). Compared to the existing fast OC FD techniques in three-phase voltage-source inverters (VSIs), this method is more cost-effective since no ultra-fast processor or high-speed measurement is required. Additionally, the method is independent of the load condition. The proposed method is only applicable to Z-source family inverters and is based on observing the effect of shoot-through (SH) intervals on the system variables during switching periods. The proposed algorithm includes two consecutive stages: OC detection and fault location identification.... 

Due to several advantages, three-phase Dual Active Bridge (DAB) converter is widely used in numerous applications nowadays. On the other hand, this converter is very vulnerable to Transistor Open-Circuit Fault (TOCF). Therefore, a fault-tolerant (FT) scheme has been proposed in this paper to solve the problem. First, normal and faulty conditions are investigated, and according to the results, a fault-diagnosis (FD) approach is introduced. Using the outcomes of FD unit, a new post-fault strategy is proposed for the converter. The FD method is based on the DC component of transformer phase currents, and the basis of FT technique is shedding the faulty phase. Some benefits of the proposed... 

In this paper, a fast and practical method is proposed for open-circuit (OC) fault diagnosis (FD) in a three-phase quasi-Z-source inverter (q-ZSI). Compared with the existing fast OC FD techniques in three-phase voltage source inverters, this method is more cost-effective since no ultrafast processor or high-speed measurement is required. Additionally, the method is independent of the load condition. The proposed method is only applicable to Z-source family inverters and is based on observing the effect of shoot-through intervals on the system variables during switching periods. The proposed algorithm includes two consecutive stages: OC detection and fault location identification. When both... 

In this article, a new soft switching isolated push-pull dc-dc converter using a three-winding transformer is proposed. The proposed hybrid resonant and pulse width modulated converter employs a conventional push-pull structure in the primary side, a voltage doubler in the secondary side, and a bidirectional switch besides the transformer, altogether help offering a high efficiency over a wide range of input and output voltage signals with an unsophisticated fixed-frequency control mechanism. The primary-side switches are commutated under zero voltage switching with low switching current and the secondary-side diodes are commutated under zero current switching. In this article, we first... 

Due to their cost-effective manufacturing and robust structure, an electromagnetic sensor called resolver is being applied in a wide range of applications, especially in those which high reliability is particularly essential. Since resolvers are usually chosen as position detector units in harsh environments, their chronic exposure to high temperature and mechanical shocks is unpreventable and accordingly, performance failure as a result of output signal winding open circuit fault (OCF) is inevitable. In this paper, a new technique is proposed to keep the performance of the resolver within an acceptable range of position error while one of the output signals (SIN/COS) is inaccessible. To... 

In the classical parametrization of the single-diode model of photovoltaic (PV) cells and modules based on the datasheet values, first, the values of the five unknown parameters of the PV model are extracted via the values of the open-circuit voltage Voc, the short-circuit current Isc, and the voltage and current at the maximum power point Vm, Im at standard test conditions (STC). Next, using some translational formulas, the STC values of the unknown parameters are projected to the new climatic conditions other than STC. A major problem of this approach is to determine the translational formulas of the five unknown parameters of the single-diode model as a function of both temperature and...