تحسين أداء الخلايا السليكونية بأستخدام المركزات الوميضية المتفلورة

Abstract

Abstract In this study the Luminescent Solar Concentrator (LSC) plates have been prepared with different concentrations (1E-5 , 2E-5 , 3E-5 , 5E-5 , 7E-5 , 1E-4 ) mol/L of (Rhodamine 6G) organic dye doped epoxy resin. The optical properties of dye, doped and un-doped epoxy, was measured. The solar-to-electric conversion efficiencies of several (LSC) modules based on (R6G) were measured. It was found that the conversion efficiency depend on dye concentration in the (LSC) . The best conversion efficiency improvement for a modules Si-solar cell of dimensions of (10cm x 20cm) covered with (LSC) had dye concentration (2E-5) was ( 7.897%) (i.e. with efficiency increment (∆η=12.3%) compared with the same module without LSC). It was found that Rhodamine (6G) doped epoxy resin exhibited properties which give it a potential to improve the (Si) solar cell performance efficiency, namely a wide absorption range (530-560) nm , (97 %) quantum yield, and the highest photo-stability of Rhodamine (6G) dye, although the overlap of the absorption and emission spectra results in reabsorption (RA) losses.

Keywords: Luminescent Solar Concentrator, Optical properties, Solar cells, Epoxy, Rhodamine (6G) dye.

Introduction The (LSC) is particularly suited this application as it is relatively inexpensive, does not require solar tracking and works in both diffuse and direct sun light. The (LSC) can be designed such that the luminescence energy matches the (PV) cell, by this way, the light reaching the cell is converted more efficiently, because the down-conversion of the radiation happens in (LSC), unwanted thermal losses in the cell are avoided. Organic dyes offer the simplest means of incorporating a fluorophore in a (LSC), as they can easily be dissolved in a range of organic polymers, such as poly methylmethacrylate (PMMA), which are then cast into sheet form. Initial (LSC) research[1], used dyes originally developed for use in dye lasers, such as Rhodamine 6G,( DCM) and Coumarin, as they were widely available and had well-characterized properties. Many visible-emitting laser [2], making them ideally suited to (LSC) use, although they have limited photo-stability. Clear epoxy resins have been used which exhibited around (30%) lower absorption in the visible region than (PMMA).This is certainly an advantage for fluorophores which may be sensitive to temperature. Unlike (PMMA) casting, which requires heat to cure the polymer, epoxy resins can set at room temperature. However, epoxy resins have a poorer photo stability compared with (PMMA).Sheet thicknesses are typically in the range (0.2-0.5) cm . This is primarily because sheet material (glass, PMMA) is readily available in these thickness, or can be produced with relative ease. Two thin sheet will lack the strength to support it over the width of the (LSC). Conversely, a thicker sheet will increase the weight and embodied energy of the (LSC) module. A thicker sheet can result in a higher efficiency , as the required fluorophore concentration can be decreased, thus reducing re-absorption losses. However, this must be balanced against the increased embodied energy and material cost. A possible disadvantage is the extremely high dye concentrations required in the thin film which may lead to quenching and a drop in quantum yield.The main advantage of thin-film device is the possibility of reducing host absorption losses in the NIR region of the spectrum by depositing the film on to a substrate such as low-iron or borosilicate glass or fused silica which have lower absorption in the NIR region than polymeric hosts such as (PMMA) or polycarbonate. Even if the thin film is made of a polymer which exhibits host absorption, the proportion of a trapped photon’s path spent inside the film is minimal. This becomes important for NIR-emitting fluorophores ,where a deuterated or fluorinated polymer may be needed to achieve a high quantum yield. Afactor which is often not considered is the flammability of many polymers , especially (PMMA). Indeed , PMMA’s high flammability is the main reason is not used for window glazing, despite its excellent optical qualities. Polycarbonate, which is self-extinguishing[3], is used instead. By using a thin film of polymer on a glass substrate, the problem of polymer flammability is eliminated.

(Δη%) it’s equal the different between conversion energy efficiency of solar cell with (LSC)(η% with LSC ) and solar cell without (LSC) (η%bare) divided by the (η% bare)

Experimental work 1- Sample preparation: 1-1- Liquid samples: The dye solution with different concentrations were prepared according to the relationship :

Where : W: Weight of the dissolved dye (g), Mw : Molecular weight of the dye(g/mol). V: The volume of the solvent (ml). C: The dye concentration (mol/l). The prepared solutions were diluted according to the following equation:-

C1 V1=C2 V2 Where: C1: primary concentration C2: the required concentration V1: the volume before dilution V2: the volume after dilution

1-2- Film sample : All LSC plates (1mm thickness, different concentrations) have been tested for homogenty by using spectrophotometer-T60 PG instruments Limited Company to carry out the absorbance and transmittance spectrum in the wavelength range (300nm-700nm) region.

Results and discussions The conversion power efficiency of bare solar cell has been measured indoor using Solar Module Analyzer PROVA 200 co, and compared with conversion power efficiency of solar cell with epoxy plate of different concentrations ,Modules with dimensions of (10cm x 20cm) and (LSC) with dye concentration (2E-5) had efficiency of (7.897%) as shown in (Fig 3) , (i.e. with efficiency increment (∆η=12.3%) compared with the same module without (LSC) . The reason for conversion power efficiency increment is the red shift in the incident light concentrate by the (LSC), in which the (Si) solar cell is more response. Absorbance and transmission spectrum of all LSC plates at different concentrations have been measured using [UV - VIS (spectrophotometer)] , Absorptions was decreased as the dye concentrations increased as shown in (Fig 1), also it was noticed a red shift in the position of the peak absorption, Transmittance of all LSC plates at different concentrations has been studied and noticed that at concentration (1E-5mol/L) transmission reach (78%) as shown in (Fig 2) and it decreased with increasing thickness and concentration of (LSC) plate[2].

Conclusions From the results of optical properties of liquid sample, it can be concluded that there is an increase in stock shift toward red region in the position of the maximum fluorescence intensity of for Rd6G with increasing in the concentration.while there is a reduction of quantum efficiency yield with increasing in the concentrations. (R6G) dye dissolve directly in epoxy resin.The (LSC) plate at concentration (2E-5mol/L) and thickness (1mm) gives the highest conversion power efficiency of solar cell.

Fig.1 . Absorption spectrum of R6G doped epoxy with different concentrations

Fig.2.Transmission spectrum of R6G doped epoxy with different concentrations

Fig. 3. I-V characteristics properties Si solar cell with LSC consist of (mol/L) dye doped epoxy References 1- J.M. Drake, M.L. Lesiecki, J. Sansregret, and W.R.L. Thomas. "Organic dyes in PMMA in a planar luminescent solar concentrator a performance evaluation". Appl. Opt., 21(6):2945–2952,(1982). 2- R. Kinderman, L.H. Slooff, A.R. Burgers, N.J. Bakker, A. Bu¨chtemann, R. Danz, and J.A.M. van Roosmalen. "I-V performance and stability study of dyes for luminescent plate concentrators". J. Sol. Energy Eng., 129:277–282, (2007). 3- B.C. Rowan, L.R. Wilson, and B.S. Richards. "Advanced material concepts for luminescent solar concentrators". IEEE J. Selected Topics in Quantum