DEVELOPMENT OF SINGLE CRYSTALLINE SILICON SOLAR CELLS LAY-DOWN - PDF document

18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS DEVELOPMENT OF SINGLE CRYSTALLINE SILICON SOLAR CELLS LAY-DOWN PROCESS ON COMPOSITES J. C. Kim 1 , I. H. Choi 2 , D. H. Kim 1 , S. K. Cheong 1 * 1 Mechanical Engineering, Seoul National Uni. of Science & Technology, Seoul, Korea Republic 2 Aerodynamics and Structures, Korea Aerospace Research Institute, Daejeon, Korea Republic * Corresponding author (skjung@seoultech.ac.kr) Keywords : CFRP composites; Single crystalline silicon solar cells; Lay-down process 1 Introduction 2.2 Bonding methods Recently, photovoltaic power energy appears to be Adhesive materials and bonding methods are very one of the major technologies for the global sheared important. There are various kinds of factors which concerns in protecting environment. Up until now, affect the structural stability for adhesively bonded many studies for the development of solar cell have solar cells to composite plates. Particularly, the focused on better stability and higher efficiency. adhesive material for aircrafts should be selected to However, the solar industry will be developed for guarantee high reliability of adhesion during the combining solar cells to various kinds of structures. flight. The secondary bonding method with three Light-weight composite is suitable for the structures types of adhesion materials (EVA film, Resin film, which need high specific strength and stiffness. Elastic adhesive) were studied in this study. Nowadays the solar cell bonding to skins of buildings, vehicles, or electrical devices is a big 2.3 Test specimen preparation issue [1]. The research paper on bonding thin-film The specimen were made of carbon fiber silicon solar cell to CFRP composite was published unidirectional prepreg and woven type of in reference [2]. However, there are many glass/epoxy. The carbon prepreg sheets were cut to possibilities for the solar cell bonding process 250 x 250 mm size and then six plies of [45/0/-45] s depending on the combination of materials. symmetric laminate were stacked and glass-epoxy In this study, the solar cell bonding method to sheets were placed on both sides. The standard composite plate was developed. Single crystalline curing process was applied [4]. Fig.3 and Fig.4 silicon solar cell was used in this study. The illustrate the test specimens with solar cell and the electrical performance of solar cell was monitored experimental setup for tensile test [1]. after applying 0.3% strain and 0.75% strain load to the specimen . Ethylene tetrafluoroethylene (ETFE) Ethylene vinyl acetate(EVA) Single crystalline silicon solar cell 2 Experiments 24.8 mm 2.1 High efficiency photovoltaic module Electrode The single crystalline silicon solar cell, which has the highest energy efficiency among various kinds of SIngle crystalline silicon solar cell solar cells, was used in this study(Fig. 1). The cells (w ith protection layer) were cut for making specimens by specific laser cutting machine to avoid any possible defect. Then Ribbon wire we coated protection layer on the top side of solar cell with ethylene tetrafluoroethylene (ETFE) and used bonding material ethylene vinyl acetate(EVA) in general usage(Fig. 2, table 1) [2,3]. Fig. 1. Schematic of solar module; (top) cross-section, (bottom) front and rear sides.

3 Test results 3.1 Electrical properties 50 Fig. 5 shows the solar modules J-V characteristics of 40 each specimen after tensile test [3]. When EAV and 2 ) Current Density, J (mA/cm Resin film were used as bonding materials, their 30 electrical performance were gradually decreased Single crystalline silicon solar module Specimen no.1 after test, whereas elastic adhesive bonding case has Specimen no.2 20 no significant decreasing trend after test. Specimen no.3 Specimen no.4 Specimen no.5 Specimen no.6 50 10 η: energy conversion efficiency Specimen no.7 η:17% Specimen no.8 40 η:13.23% 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 2 ) Current Density, J (mA/cm η:7.6% Voltage(V) 30 Fig. 2. Performance characterization of as-received single crystalline silicon solar module. 20 EVA film V oc (V) J sc (mA/cm 2 ) Fill factor Efficiency(%) As-received 10 After tensile test(0.3% strain) 0.65 44.01 0.6241 17.49 Avg. After tensile test(0.75% strain) Table 1 The average performance of as-received single crystalline 0 silicon solar modules. 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Voltage(V) 50 η: energy conversion efficiency η:17% 40 η:13.7% 2 ) Current Density, J (mA/cm η:10.15% 30 20 Resin film As-received 10 After tensile test(0.3% strain) After tensile test(0.75% strain) 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Voltage(V) 50 η: energy conversion efficiency Fig. 3. Description of test specimen. η:18.12% η:17.87% 40 η:17.91% 2 ) Current Density, J (mA/cm 30 20 Elastic Adhesive As-received 10 After tensile test(0.3% strain) After tensile test(0.75% strain) 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Voltage (V) Fig. 5. Performance characteristics of a solar modules after tensile test; (top) EVA film; (middle) Resin film; (bottom) Elastic adhesive. Fig. 4. Experimental setup for tensile test .

` 3.2 Adhesive thickness control Figure 5 shows that the elastic adhesive is suitable for bonding material. Figure 6 shows the effect of 50 η: energy conversion efficiency , FF: fill factor adhesive thickness on electrical performance after η: 19.61% applying load. FF: 0.6616 40 2 ) Current Density, J (mA/cm 50 η: energy conversion efficiency , FF: fill factor 30 η: 19.51% FF: 0.6554 40 20 2 ) Current Density, J (mA/cm 30 10 Elastic Adhesive 460 micron (0.75% strain) 20 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Voltage (V) 10 Elastic Adhesive 120 micron (0.75% strain) 50 0 η: energy conversion efficiency , FF: fill factor 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 η: 21.22% Voltage (V) FF: 0.6752 40 2 ) Current Density, J (mA/cm 50 30 η: energy conversion efficiency , FF: fill factor η: 19.00% FF: 0.6534 40 20 2 ) Current Density, J (mA/cm 30 10 Elastic Adhesive 570 micron (0.75% strain) 20 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Voltage (V) 10 Elastic Adhesive Fig. 6. Performance characteristics of solar modules various adhesive 240 micron (0.75% strain) thickness at 0.75% strain (120μm, 240μm , 360μm , 460μm , 570μm). 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Voltage (V) 4 Summaries 50 The single crystalline silicon solar module lay-down η: energy conversion efficiency , FF: fill factor η: 19.82% process was developed on the CFRP using the FF: 0.6565 40 secondary-bonding method. Elastic adhesive 2 ) Current Density, J (mA/cm material was suitable for maintaining good electrical 30 performance regardless of loading or adhesion thickness. The basic principles for bonding brittle 20 silicon cell to the various kinds of structural surface can be predicted. Further study will be performed 10 under various temperature conditions. Elastic Adhesive 360 micron (0.75% strain) 0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Voltage (V)

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