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Showing 8 results for Solar Cells

Prof. Abbas Behjat, Mrs Naeimeh Torabi, Mrs Fatemeh Dossthosseini,
Volume 8, Issue 1 (1-2014)
Abstract

By introducing a thin ZnO layer as an optical spacer, we have demonstrated that inserting this layer between an active layer and a reflective electrode results in a re-distribution of the optical electric field inside bulk heterojunction solar cells. A theoretical analysis by optical modeling showed that the thin ZnO layer could shift the position of the maximum of the electric field into the absorbing layer. Theoretical calculations were compared with experimental results for devices with and without an optical spacer. By using a ZnO optical spacer layer, a significant increase was observed in the short circuit current density of J-V curves. This increase might be due to harvesting more lights and also hole-blocking by the ZnO layer. Both electrical and optical characteristics of the device provided improved results in the power conversion efficiency of the bulk heterojunction solar cell up to 3.49%.
Dr. Abbas Behjat, Mehdi Dehghani, Fariba Tajabadi, Nima Taghavinia,
Volume 9, Issue 1 (1-2015)
Abstract

Planar superstrate CuInS2 (CIS) solar cell devices are fabricated using totally solution-processed deposition methods. A titanium dioxide blocking layer and an In2S3 buffer layer are deposited by the spray pyrolysis method. A CIS2 absorber layer is deposited by the spin coating method using CIS ink prepared by a 1-butylamine solvent-based solution at room temperature. To obtain optimum annealing temperature, these layers are first annealed at 150°C and then annealed at 210°C, 250°C and 350°C respectively. The optimum annealing temperature of the layer is found to be 250°C, where 23 mA current density and 505 mV open circuit voltage are measured for the best fabricated solar cell sample.
Hamzeh Nourolahi, Mohammad Agha Bolorizadeh, Abbas Behjat,
Volume 11, Issue 1 (1-2017)
Abstract

Nanostructures of noble metal materials have been used in organic solar cells for enhancement of performance and light trapping. In this study, we have introduced branched silver cauliflower-like nanopatterns as sub-wavelength structured metal grating in organic solar cells. Self-assembled fabrication process of branched nanopatterns was carried out on a bio-template of cicada wing nanonipple arrays using a gas aggregation dc magnetron sputtering nanocluster source without size filtration. The branched nanostructures provide surface gaps with dimensions near the organic exciton diffusion length, which prevents recombination of charge carriers. An increased power conversion efficiency of 14.8% compared to that of the planar device was achieved mainly due to the enhancement in the short-circuit current density. Besides, these branched cauliflower-like nanopatterns had enhanced optical light absorption in the solar cell as a result of enhancing the optical path length of the reflected light in the active layer and plasmonic effects of the noble metal material.


Farshad Farhadnia, Ali Rostami, Samiye Matloub,
Volume 11, Issue 2 (8-2017)
Abstract

In this article, the effect of plasmonics properties of metal nanorods and nanoparticles on solar cell performance were investigated and simulated. Due to the classic solar cell disadvantages, it seems that a plasmonic solar cell is one of these methods. In plasmonic solar cells, because of plasmonic effect, a high electric field builds around metal nanoparticles so that high conversion efficiency is available. In this study, it is shown that the near-field electromagnetic wave severely affects the generation rate, which handles the carrier’s generation in the solar cell equations. By manipulating the plasmonic properties of nanoparticles or nanorods in solar cells structure, distribution of the electromagnetic fields are altered. In this work, optical power and generation rate related to the poynting vector is calculated. So, for improving the generation rate as an important parameter in solar cells, the alteration of nanoparticles or nanorods material, shape, inter-distance between them and medium material, are done. Finally, the comparison between classical solar cell and our improved structure is performed.


Hadi Zarei, Rasoul Malekfar,
Volume 12, Issue 1 (1-2018)
Abstract

In this paper, tetragonal chalcopyrite (CIGS) Cu(InxGa1-x)Se2 with x=0, 0.5, 0.8, 1 are synthesized by heating-up method. These nanoparticle structures differ in morphology and absorption properties due to the synthesis temperatures of 250, 255, 260, 265, 270 and 280 ºC, and gallium molar ratio over the total gallium and indium contents. These features are studied using scanning electron microscope, X-ray diffraction and absorption spectroscopy in visible, ultra-violet and near-infrared wavelengths. Results indicate that by increasing gallium content, absorption edge rises toward the visible light. Any modification in the absorption edge changes the band gap and as a result the energy gap and the absorption of cell increases considerably. Also in the heating-up method, increasing the reaction temperature improves nanoparticles crystallites. This leads the absorption improvement and higher cells efficiency. Produced nanoparticles are spherical shape with are varying the diameter around 30-80 nm.


Naemeh Aeineh, Nafiseh Sharifi, Abbas Behjat,
Volume 12, Issue 2 (12-2018)
Abstract

To investigate the plasmonic effect in perovskite solar cells, the effect of depositing Au@SiO2 nanoparticles on the top and the bottom of mesoporous TiO2 layers was studied. First, Au@SiO2 nanoparticles were synthesized. The particles were then deposited at the different interfaces of mesoporous TiO2 layers. Although the two structures show approximately similar optical absorption, only cells with Au@SiO2 nanoparticles deposited at the bottom of the mesoporous TiO2 layers demonstrated an improved photocurrent performance compared to the reference cells. This structure shows a short-circuit current density (JSC) of 20.7 mA/cm2 and open circuit voltage of 1081 mV. This enhancement may be attributed either to the interface surface engineering or plasmonic resonance of Au@SiO2 nanoparticles depends to the NPs size and position.  


Elham Karimi, Seyed Mohamad Bagher Ghorashi, Maryam Hashemi,
Volume 14, Issue 1 (1-2020)
Abstract

Recently, organo–metal halide perovskites have attracted much attention of the scientific community relating to their successful application in the absorber layer of low-cost solar cells. However, enough is known about the material and device properties, to realize that much remains to be learned.
In this paper, the electrical and optical properties of perovskite solar cells are investigated using the COMSOL Multiphysics simulation program. It is a study of the influences of carrier diffusion length (L), dielectric constant (εr), the valence band offset (VBO) of absorber/hole transport materials (HTM) and illumination intensity on fill factor (FF), short-circuit current density(JSC), performance (PCE), and open-circuit voltage(VOC). Also, J-V characteristics are calculated for different εr values. The simulation results point to the great dependence of efficiency on the carrier diffusion length of absorber layers. It is shown that, to obtain a high rate of efficiency, the relative permittivity should not be higher than 45.
 
Asieh Nazari Mofrad, S.m. Bagher Ghorashi, Farhad Jahantigh,
Volume 15, Issue 1 (1-2021)
Abstract

One of the main challenges for perovskite solar cell (PSCs) structures is their high sensitivity to humidity and ambient temperature, which significantly lowers the lifespan of these devices. Low stability of this devices is considered one of the principal limitations to make them commercialized. To increase the stability of the solar cell is to encapsulate the solar cell. The encapsulation is to cover the device with a non-reactive material, which prevents the penetration of ambient moisture and increases the thermal stability of the cell. If the uncoated device is exposed to continuous incident light for several hours, its structure is damaged while encapsulated device has a longer duration time. Several methods have been proposed for encapsulating a perovskite solar cell. The principal strategy of these methods involves deposition of a thin layer of polycarbonate polymer on the perovskite solar cell structure, resulting in layers of the desired structure. After fabrication and encapsulation process, the order of the various layers are FTO / bl-TiO2 / mp-TiO2 / Perovskite (CH3NH3PbI3) / Spiro-OMETAD / Au / Polycarbonate Polymer. To increase the effective stability, the glass coating is placed on the polycarbonate polymer. After acquiring sufficient adhesion between the glass coating and the polymer layer on the structure of PSCs, UV epoxy is used to seal the whole structure. Having performed the encapsulation, the samples were exposed every day to 85% constant humidity and 85°C temperature for 10 hours and it was observed that the cell efficiency, under the mentioned conditions and after successive measurements, maintained to a high extent.

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