Interlayer Effect: Si-based Double Junction Tandem Solar

Inter mould Effect Si-establish Double Junction Tandem solarInvestigation of Interlayer Effect on Si-based Double Junction Tandem solar CellAbstract Silicon-based two-fold concurrence tandem bicycle solar carrellular teleph iodin was fabricated and simulated victimization wxAMPS softw atomic chassis 18. Nano structure of SiO2/ Si3N4 interlayer was inserted amid the silicon and InGaN sum to investigate the effect on the quantum cogency of the Si-based solar cubicle. The quantum dexterity characterizations were fecesvas under AM1.5 solar spectrum at 300o K. SiO2 was found to be an ex jail carrelent interlayer for Si-based double combination tandem solar cell comp atomic number 18d to Si3N4 and record better quantum efficiency. The rise to power of SiO2 and Si3N4 nano structure interlayer between the Si and InGaN improved the Jsc by 5.79% and 2.21% respectively compared to the absence of interlayer.Key-Words Silicon solar cell, interlayer, silicon dioxide, silicon nit ride, quantum efficiency, wxAMPS1Introduction out-of-pocket to its low fabric cost and ease of manufacturing, silicon-based solar cells are preferent for muscle conversion. Advances in the engineering science have earthshakingly improved the boilers suit performance of silicon solar cells. Besides, Si has better cooling faculty compared to sapphire 1. Si has bragging(a)r thermal conductivity which promises much winged thermal dissipation 2. Since solar cells operate under in high spirits temperature, this singularity is strongly desired. Indium gallium nitride (InGaN) is one of the best semiconductor materials for optoelectronics which can operate in high-temperature. In addition, InGaN is a widely used for multi-junction tandem solar cells with high conversion efficiency and shown a better resistivity to radiation damage compared to other materials. It provides variety of band gap energies as the band gap changes with the In-Ga ratio. Due to its potential in cost drop -off and faster thermal dissipation, researchers are committed to study InGaN-on-Si technologies.As Si and InGaN is having large relative lattice mismatch, the conversion efficiency of the device is limited. This materialization leads to phase separations. Because of that, suitable interlayer or absorber layer is desired to ensure individually layer to match. Thermal lattice mismatch was reported by Krost et. al in 2002 stating that cracking of GaN on Si usually occurs due(p) to the large thermal mismatch of GaN. The thermal stress can be cut back significantly by insertion of low-temperature AlN interlayers, introducing multiple AlGaN/GaN interlayers, and growing on prepatterned substrates 3.The embrasure traps at the nitride/Si interface exhibit dissimilar properties from those at the SiO2/Si interface in some aspects. Thermally grown SiO2, the genuinely constituted gate dielectric for Si-based MOS devices, possesses remarkable electronic properties that are unmatched by o ther materials. Both SiO2 and Si3N4 are equally transparent redden for high energy knock against UV band of solar spectrum. SiO2 is highly technically established materials as a passivation layer for Si based MOS applied science and it may also be used for integration of PD technology 4. Si3N4 is also potential coating materials against degradation of detecting device even in high radiation environment and temperature 5.Implementation of double junction solar cell is one of the alternatives in enhancing the production characteristic of solar cell 6. Users demand a better efficiency and high output current of solar cell. Thus, we investigated the structure of InGaN-on-Si solar cell with the presence of polar interlayer (SiO2 and Si3N4) which was inserted between Si and InGaN layer to intensify the light conversion in the cell. This structure enables the increase of current of both prime and fathom cell by reducing the recombination effects 7. In this paper, we focused on the quantum efficiency which is one of the criteria that must be considered as we can evaluate the quantity of current that the cell will produce when exposed to sunlight.2data-based ProcedureThe structure as shown in the Fig. 1 was fabricated utilise wxAMPS software which was developed by Prof. Rockett and Dr. Yiming Liu of UIUC and Prof. Fonash of PSU. The solar cells were grown on a n- part silicon substrate. Three different experiments have been conducted without interlayer, with SiO2 interlayer and with Si3N4 interlayer.Fig. 1- Structure of the solar cellComposition of In0.4Ga0.6N with Eg=1.99 eVwas used in all three experiments. The output characteristics were canvas under AM1.5 solar spectrum at 300oK. InGaN is chemically a n-type semiconductor because of the presence of nitrogen in the composition. Mg is used to dope the InGaN in sound out to make it p-type 8.3Result and DiscussionFig. 1 presents the internal quantum efficiency of the three conducted experiments.Fig. 2- Int ernal Quantum EfficiencyFrom Fig. 2, insertion of SiO2interlayer shows better IQE compared to Si3N4 and without interlayer. The difference in the IQE can be seen at high energy spectrum. The difference is due to the recombination at the surface of the cells. When attack aircraft carriers are generated near the surface, and since blue light for theoretical account is absorbed very close to the surface, quantum efficiency at high energy edge which absorbed very close to the surface will be alter by the front surface recombination. Presence of interlayer leads to a higher generation rate and it is more significant at the wavelength 2/ Si3N4is introduced between the Si and InGaN layer, the absorption is further improved and enhances the diffusion length. The highest quantum efficiency is put down at the wavelength of 650-700 nm. The surface recombination and diffusion length in the bottom cell tends to shift the peak to pull down energy edge. The properties of SiO2 and Si3N4 itself differs from each other. SiO2 has a refractive index of 1.57 while Si3N4 with refractive index of 2.05. SiO2 permits selective diffusions into silicon wafer.Fig. 3- ongoing density without interlayerSince the solar cells are made up of p-type and n-type semiconductors, electrons from the n-region near the pn junctionlikely to diffuse into the p region. As these electrons diffuse, positively charged ions (donors) are left in the n-region. On the other hand, holes from the p-type region near the pn junction start to diffuse into the n- region. As we analyze the current density behavior based on the structure in Fig. 1, the bottom cell (Si) which is stacked with InGaN layer determines the current density with the presence/absence of interlayer. It can be seen that recombination that occur in the bottom cell affected its total performance. Besides, the in-plane lattice mismatch between Si and InGaN was reported by Henini in his book. accept growth of InGaN layer on Si (without damp or interlayer) gives in-plane mismatch from -7.81% to -17% depending on the content of Indium and Gallium 9. Direct growth of InGaN on Si makes some part of the InGaN diffused into the Si. immune carrier recombinations at localized states arise due to this lattice mismatch which leads to lower Jsc. Besides, cracking of GaN on Si usually occurs due to the large thermal mismatch of GaN. This lattice mismatch effect can be minify by inserting interlayer which can reduce the thermal stress between the junction of InGaN and Si. GaN-based semiconductor is not well suited for direct growth on Si.Fig. 4- on-line(prenominal) density for Si3N4 interlayerFrom Fig. 4, the behavior of the current density with Si3N4 interlayer is almost the aforementioned(prenominal) with no interlayer but it gives lower recombination rate hence produces greater current-density compared to the one in Fig. 3. At 0.08 m-0.1 m, it can be observed that Jn and Jp stay incessant at a deeper position from the bott om cell. The final alignment and mapping of InGaN cell is strongly dependent on the starting substrate type, orientation, substrate pre-treatment, type of buffer or inter layer and growth conditions. high-pitched recombination rate as shown in Fig.3 and Fig. 4 is not desired. Thus, Si3N4 is not so suitable to be used as an interlayer between Si and InGaN.Fig. 5- Current density SiO2 for interlayerFig. 5 shows the current density at the bottom cell when SiO2 is used as interlayer. Unlike Si3N4, cells with SiO2 as its interlayer give less recombination rate. The type and magnitude of recombination processes in the cell greatly affected the minority carrier lifetime and the diffusion length. The recombination rate will depend on the number of defects present in the material. Defects here may refer to the doping concentration, dopants or the properties of the material itself. Less interface defects are shown by SiO2 and this is proven by nowadays Si fabrication technology which uses SiO2 as gate interface. Even though both SiO2 and Si3N4 are equally transparent for high energy edge of solar spectrum, but the interface traps at the nitride/Si interface exhibit contradictory properties from those at the SiO2/Si interface in some aspects.no(prenominal)interlayerSiO2 interlayerSi3N4 interlayerVoc (V)1.58861.63711.5912Jsc (mA/cm2)6.47066.84546.6136FF (%)48.43952.213048.8326Efficiency (%)4.97915.85135.1390Table 1- Output characteristics of the solar cell based on different interlayerThe output characteristics as shown in Table 1 are relatively important in determining the performance of solar cells based on different interlayer. It can be seen that SiO2gives a higher Voc, Jsc, ingurgitate factor and efficiency compared to Si3N4. The addition of SiO2/Si3N4 nano structure interlayer between the Si and InGaN improves the Jsc by 5.79% and 2.21% respectively compared to the absence of interlayer.4ConclusionThe effect of different interlayer on Si-based solar cell is stud ied. InGaN is not well suited fordirectgrowthonsiliconsubstrate. SiO2 has shown to be an exquisite interlayer between Si and InGaN cell. It appears that suitable choice of interlayer is important to match the top cell and the bottom cell. The interlayer also will give a significant effect on its quantum efficiency and total current density.5 mentionI would like to thank Pusat Penyelidikan dan Inovasi UMS and Kerajaan Malaysia for the funding of this project (Project code FRG0307-TK-1/2012).ReferencesC.Y.Liuet al.,Nitride-based concentrator solar cells grown on Si substrates, solar brawn Materials solar Cells117(2013)5458Miro Zeman Janez Krc. Electrical and Optical Modelling of Thin-Film Silicon solar Cells.MRS Proceedings. Vol. 989. No. 1. Cambridge University Press, 2007.Krost, Alois, and Armin Dadgar. 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