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A concept for Lithography-free patterning of silicon heterojunction back-contacted solar cells by laser processing  [PDF]
Bugra Turan,Kaining Ding,Stefan Haas
Physics , 2015,
Abstract: Silicon heterojunction (SHJ) solar cells with an interdigitated back-contact (IBC) exhibit high conversion efficiencies of up to 25.6%. However, due to the sophisticated back-side pattern of the doped layers and electrode structure many processing and patterning steps are required. A simplification of the patterning steps could ideally increase the yield and/or lower the production costs. We propose a patterning approach for IBC SHJ solar cells free of any photo-lithography with the help of laser-induced forward transfer (LIFT) of the individual layer stacks to create the required back-contact pattern. The concept has the potential to lower the number of processing steps significantly while at the same time giving a large degree of freedom in the processing conditions optimization of emitter and BSF since deposition of the intrinsic/doped layers and processing of the wafer are all independent from each other.
The Effects of Fabrication Prameters and Electroforming Phenomenon on CdTe/Si (p) Heterojunction Photovoltaic Solar Cell  [PDF]
Wagah F. Mohammad
Circuits and Systems (CS) , 2012, DOI: 10.4236/cs.2012.31007
Abstract: The In-doped CdTe/Si (p) heterostruture was fabricated and its electrical and photoelectrical properties were studied and interpreted. During the fabrication processes of CdTe/Si heterojunction, some practical troubles were encountered. However, the important one was the formation of the SiO2 thin oxide layer on the soft surface of the Si during the formation of the back contact. The silicon wafer was subjected to different chemical treatments in order to remove the thin oxide layer from the silicon wafer surfaces. It was found that the heterojunction with Si (p+) substrate gave relatively high open circuit voltage comparing with that of Si (p) substrate. Also an electroforming phenomenon had been observed in this structure for the first time which may be considered as a memory effect. It was observed that there are two states of conduction, non-conducting state and conducting state. The normal case is the non-conducting state. As the forward applied voltage increased beyond threshold value, it switches into the conducting state and remains in this state even after the voltage drops to zero.
Morphological and optical characteristics of porous silicon produced by anodization process in HF-acetonitrile and HF-ethanol solutions
Miranda, Cláudia R. B.;Baldan, Maurício R.;Beloto, Antonio F.;Ferreira, Neidenêi G.;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000400022
Abstract: porous silicon (ps) samples were obtained by anodization etching process of n-type silicon wafer phosphorus-doped. electrochemical oxidation of ps was investigated in aqueous hydrofluoric acid (hf) containing additive such as ethanol or acetonitrile. pore formation was studied with the variation of type and resistivity of the silicon wafer, taking into account the most important anodization process parameters such as: acid concentration, current density and anodization time. scanning electron microscopy (sem) and raman scattering spectroscopy measurements were used to characterize the macropore morphology changes and sample photoluminescense responses, respectively. ps layer formed in hf-acetonitrile solution showed more uniform and homogeneous macropore distributions with different shapes and sizes. behavior may be explained because acetonitrile surface tension is greater than that of ethanol. therefore, acetonitrile molecules might passivate the silicon surface dissolved during the anodization process.
Photo-EMF Sensitivity of Porous Silicon Thin Layer–Crystalline Silicon Heterojunction to Ammonia Adsorption  [PDF]
Yuriy Vashpanov,Jae Il Jung,Kae Dal Kwack
Sensors , 2011, DOI: 10.3390/s110201321
Abstract: A new method of using photo-electromotive force in detecting gas and controlling sensitivity is proposed. Photo-electromotive force on the heterojunction between porous silicon thin layer and crystalline silicon wafer depends on the concentration of ammonia in the measurement chamber. A porous silicon thin layer was formed by electrochemical etching on p-type silicon wafer. A gas and light transparent electrical contact was manufactured to this porous layer. Photo-EMF sensitivity corresponding to ammonia concentration in the range from 10 ppm to 1,000 ppm can be maximized by controlling the intensity of illumination light.
Simulation analysis of the effects of a back surface field on a p-a-Si:H/n-c-Si/n+-a-Si:H heterojunction solar cell
Simulation Analysis on Effects of Back Surface Field on p-a-Si:H/n-c-Si/n+-a-Si:H Heterojunction Solar Cell

Hu Yuehui,Zhang Xiangwen,Qu Minghao,Wang Lifu,Zeng Tao,Xie Yaojiang,

半导体学报 , 2009,
Abstract: In order to investigate the effects of a back surface field (BSF) on the performance of a p-doped amor-phous silicon (p-a-Si:H)/n-doped crystalline silicon (n-c-Si) solar cell, a heterojunction solar cell with a p-a-Si:H/n-c-Si/n+-a-Si:H structure was designed. An n+-a-Si:H film was deposited on the back of an n-c-Si wafer as the BSF. The photovoltaic performance of p-a-Si:H/n-c-Si/n+-a-Si:H solar cells were simulated. It was shown that the BSF of the p-a-Si:H/n-c-Si/n+-a-Si:H solar cells could effectively inhibit the decrease of the cell performance caused by interface states.
Determination of Oxygen Concentration in Heavily Doped Silicon Wafer by Laser Induced Breakdown Spectroscopy
JI Zhen-Guo, XI Jun-Hua, MAO Qi-Nan
无机材料学报 , 2010, DOI: 10.3724/sp.j.1077.2010.10074
Abstract: Laser-induced breakdown spectroscopy (LIBS) has been applied to determine the oxygen concentration in heavily doped silicon wafer by using a high power pulsed laser and an optical fibre coupled CCD spctrometer. The relative concentration of oxygen in the heavily doped silicon wafer was calculated by the ratio of the integral intensity of the OI emission of oxygen to the SiI emission silicon from the LIBS spectra. A calibration curve was obtained by comparing the oxygen concentration determined by LIBS with the oxygen concentration determined by conventional FTIR technique used in Si industies, in which a set of four lightly doped CZ silicon wafers were used. Based on the calibration curve, quantitative oxygen concentration in several heavily doped silicon samples was measured.
Photocurrents in a Single InAs Nanowire/ Silicon Heterojunction  [PDF]
Andreas Brenneis,Jan Overbeck,Julian Treu,Simon Hertenberger,Stefanie Mork?tter,Markus D?blinger,Jonathan J. Finley,Gerhard Abstreiter,Gregor Koblmüller,Alexander W. Holleitner
Physics , 2015, DOI: 10.1021/acsnano.5b03017
Abstract: We investigate the optoelectronic properties of single indium arsenide nanowires, which are grown vertically on p-doped silicon substrates. We apply a scanning photocurrent microscopy to study the optoelectronic properties of the single heterojunctions. The measured photocurrent characteristics are consistent with an excess charge carrier transport through mid-gap trap states, which form at the Si/InAs heterojunctions. Namely, the trap states add an additional transport path across a heterojunction, and the charge of the defects changes the band bending at the junction. The bending gives rise to a photovoltaic effect at a small bias voltage. In addition, we observe a photoconductance effect within the InAs nanowires at large biases.
The Compromise Condition for High Performance of the Single Silicon Heterojunction Solar Cells
Youngseok Lee,Vinh Ai Dao,Sangho Kim,Sunbo Kim,Hyeongsik Park,Jaehyun Cho,Shihyun Ahn,Junsin Yi
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/283872
Abstract: For optimum performance of the hydrogenated amorphous silicon/crystalline silicon (a-Si : H/c-Si) heterojunction solar cells, featuring a doping concentration, localized states, as well as thickness of emitter layer are crucial, since Fermi level, surface passivated quality, and light absorption have to be compromised themselves. For this purpose, the effect of both doping concentration and thickness of emitter layer was investigated. It was found that with gas phase doping concentration and emitter layer thickness of 3% and 7 nm, solar cell efficiency in excess of 14.6% can be achieved. For high gas phase doping concentration, the degradation of open-circuit voltage as well as cell efficiency was obtained due to the higher disorder in the emitter layer. The heavily doped along with thicker in thickness of emitter layer results in light absorption on short wavelength, then diminishing short-circuit current density.
Transfer of Thin Epitaxial Silicon Films by Wafer Bonding and Splitting of Double Layered Porous Silicon for SOI Fabrication

ZHU Shi yang,LI Ai zhen,HUANG Yi ping,

半导体学报 , 2001,
Abstract: A double layered porous silicon with different porosity is formed on a heavy doped p type Si(111) substrate by changing current density during the anodizing.Then a high quality epitaxial mono crystalline silicon film is grown on the porous silicon using an ultra high vacuum electron beam evaporator.This wafer is bonded with other silicon wafer with a thermal oxide layer at room temperature.The bonded pairs are split along the porous silicon layer during subsequent thermal annealing.Thus the epitaxial Si film is transferred to the oxidized wafer to form a silicon on insulator structure.SEM,XTEM,spreading resistance probe and Hall measurement show that the SOI structure has good structural and electrical quality.
Effect of roughness and wettability of silicon wafer in cavitation erosion
NaNa Jiang,ShiHan Liu,DaRong Chen
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0375-5
Abstract: Material damage of silicon wafer with different roughness and wettability was investigated by using the self-made vibration cavitation apparatus in de-ionized water. Various roughness and wettability of silicon wafer were achieved by changing their morphology and depositing Au, diamond-like carbon films (DLC films) on them. Surface morphology was observed with a scanning electron microscope (SEM) and a surface profilometer, and wettability was characterized by the contact angle measurement. The cavitation erosion results showed that many tiny pits and cracks appeared on the wafer surface as a result of brittle fractures; the number and size of the pits and cracks increased with experiment time, which made material flake away finally; cavitation occurred more easily on the silicon wafer surface with the augment of roughness or contact angle by changing surface morphology or depositing Au, DLC thin film on it, which consequently aggravated cavitation damage.
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