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The gap between laboratory scale and commercial silicon solar cells is wider, as many processes are not being practiced in commercialization. In this work, we have investigated the silicon solar cell fabrication process followed by industries and proposed a simplified process. The fabrication process for the emitter layer, 100 nm thin film anti-reflection coating and wet oxide passivation in a single chamber diffusion furnace on 200 micron p-type mono crystalline silicon wafer was followed. The diffusion process was carried out in an atmospheric furnace using phosphorus oxychloride as dopant source, oxygen for anti-reflection coating and wet oxide surface passivation. Topographical, optical and electrical characterization were conducted to understand the properties of the above layers for application in solar cell fabrication. The reflectivity and average sheet resistivity data of the diffused wafer is in the range those published in literature. Following the procedure, number of process steps, instrument and cost of commercial solar cell fabrication can be optimized.

Thin film of oriented crystalline intrinsic polysilicon films were grown on alkali-free borosilicate glass substrate using hot-wire chemical-vapor-deposition (HWCVD) technique. A layer as a source of phosphorus dopant on top of intrinsic polysilicon films were introduced in two different approaches: (i) spinon one-micrometer-thick phosphorus dopant and (ii) phosphorus ion implantation. We investigate thepossibility of dopant diffusion, activation, and annealing, using the irradiation of 1064 nm wavelengthinfrared laser. The annealing is performed under various conditions. The laser power and scan speed are varied to ensure the suitable laser annealing condition. We carry out resistivity measurementsto validate the laser annealing process. For structural investigation, we use several characterizationtechniques, such as scanning electron microscopy, high-resolution X-ray diffraction, photoluminescence spectroscopy, and confocal Raman spectroscopy measurements. We use optical transmissionspectra for determining optical characteristics of the film. The electrical measurement shows that thephosphorous-dopedn-type polysilicon films are suitable as an emitter layer in photovoltaic device.

The impurity concentration is a crucial parameter for semiconductor thin films. Evaluating the impurity distribution in silicon thin film is another challenge. In this study, we have investigated the doping concentration of boron in silicon thin film using time of flight secondary ion mass spectrometry in dynamic mode of operation. Boron doped silicon film was grown on i) p-type silicon wafer and ii) borosilicate glass using hot wire chemical vapor deposition technique for possible applications in optoelectronic devices. Using well-tuned SIMS measurement recipe, we have detected the boron counts 101~104 along with the silicon matrix element. The secondary ion beam sputtering area, sputtering duration and mass analyser analysing duration were used as key variables for the tuning of the recipe. The quantitative analysis of counts to concentration conversion was done following standard relative sensitivity factor. The concentration of boron in silicon was determined 1017~1021 atoms/cm3. The technique will be useful for evaluating distributions of various dopants (arsenic, phosphorous, bismuth etc.) in silicon thin film efficiently.

Sun light as a renewable energy resource is getting popular day by day. Power production from a solar power plant is extensively dependent on the weather condition, daylight duration, available sunlight, air quality etc. Thus installation of large scale solar power plant requires long term feasibility study, previous five years weather data, lifetime of the solar panel, projected maintenance requirement and man power. In this survey we have visited several sites of roof top solar power plants in the Dhaka city which are aged at least five years. Firstly, we have conducted visual study of the solar panels on the roof top for visible degradation due to environment and ageing. Then we have measured Current-Voltage characteristics under sun light using portable PV-200 Seaward I-V Tracer. The Current-Voltage data were analyzed using ‘Seaward Solar Chart’ data analysis tool. The tool was used to plot Current-Voltage and Power-Voltage curves. From the data we have estimated the Standard Test Condition (STC) power, Fill Factor (F.F) and Efficiency of selected photovoltaic modules. To get a clear view over the experience of installed rooftop solar photovoltaic modules in Dhaka city, the data will be useful. The data will help us to project the challenges and provide a guide line to maintain an economically viable solar photovoltaic installation

Boron-doped polycrystalline silicon film was synthesized using hot wire chemical vapor deposition technique for possible application in photonics devices. To investigate the effect of substrate, we considered Si/SiO2, glass/ITO/TiO2, Al2O3, and nickel tungsten alloy strip for the growth of polycrystalline silicon films. Scanning electron microscopy, optical reflectance, optical transmittance, X-ray diffraction, and I-V measurements were used to characterize the silicon films. The resistivity of the film was 1.3 &times, 10&minus, 2 W-cm for the polycrystalline silicon film, which was suitable for using as a window layer in a solar cell. These films have potential uses in making photodiode and photosensing devices.

We have investigated the crystallinity of silicon film grown on glass substrate using hot wire chemical vapour deposition technique. In this study, we have grown intrinsic and phosphorous doped silicon thin film. The phosphorous doped ntype silicon films were prepared by doping intrinsic polycrystalline silicon film in two approaches. One approach used i) spin-on phosphorous dopant and the other approach used ii) phosphorous ion implantation. These films were annealed using 1064 nm infrared laser. Evaluation of crystallinity was performed by Raman spectroscopy with 514.5 nm excitation and Raman Imaging tool with 532 nm excitation. A large degree of non-homogeneity observed in the crystallinity of laser irradiated silicon film. This may be due to non-uniform melting and solidification of silicon film during laser annealing.

Large grain polycrystalline silicon thin film on low cost and robust substrate is an interesting area of research for photovoltaic devices. This film can be used to fabricate solar cell which has a potential to achieve 20% efficiency like multi crystalline silicon solar cell with the advantage of thin film fabrication techniques. In this thesis we have investigated the possibility of growing large grain (220) oriented poly crystalline silicon films, 2 to 3 micron thick, from silane‐hydrogen mixture, by hot wire chemical vapour deposition (HWCVD). Several substrates i) Si/SiO2, ii) TiO2 layer on glass, iii) textured nickel‐5% tungsten metal strip, iv) crystalline sapphire and v) alkali free borosilicate glass have been used in this work. The growth of intrinsic poly crystalline silicon film was performed starting with a thin nucleation layer at 400C followed by the thickening stage at 600C with higher silane concentration. We have optimized the growth conditions and one micron of well passivated hydrogenated (220) oriented polycrystalline film were grown successfully. We have used several characterization techniques for the evaluation of the optical, topographical and electrical properties of the film. The growth of boron doped poly crystalline and amorphous silicon film was also performed following by process similar to that used for intrinsic poly silicon film using HWCVD with the addition of diborane to the gas mixture for boron doping the silicon. The HWCVD system used for the synthesis of intrinsic and p‐type polycrystalline silicon films did not have provision for n‐type doping. For synthesis of phosphorous doped n‐ type silicon film, we initially explored doping intrinsic polycrystalline silicon film by using two different sources of phosphorous followed by Laser annealing. One approach used i) spin‐on phosphorous dopant film about one micron thick and the other approach used ii) phosphorous ion implantation. For both these approaches, we have investigated the possibility of dopant activation by irradiation with infrared continuous wave laser which can uniformly scan the sample along X‐Y directions. Laser annealing is performed varying the laser power and scan speed to ensure suitable laser annealing condition. Sheet resistivity measurement was carried out to verify the laser annealing process. In this case the several characterization techniques were also followed for the evaluation of the optical, topographical and electrical properties of the film. ‐ 9 ‐ However, the n‐type silicon films synthesised in this manner were not device quality. At this stage, we got access to another HWCVD reactor equipped with synthesis of n‐type silicon using phosphine as the dopant gas. After the above growth experiments, we took initiative to stack all these silicon layers in order to apply them in photovoltaic application. In this case we have fabricated an n‐i‐p structure on glass using two different HWCVD systems, starting with synthesis n‐type silicon on glass in one reactor. This was transferred to the second HWCVD reactor for the synthesis of intrinsic polycrystalline silicon film. After this, a combination of a thin layer of amorphous intrinsic silicon followed by p‐type amorphous silicon film was deposited to form a hetero junction between the intrinsic polycrystalline silicon and p‐type amorphous silicon layer. The structure is well known as heterojunction with intrinsic thin layer (HIT). In our case the intrinsic polycrystalline silicon layer acts as the light absorber layer, the top p‐type amorphous silicon acts as emitter layer, while the bottom n‐type silicon acts as back surface field. The performance of the device was evaluated from dark and illuminated I‐V characterization. It was observed that the light response was very weak. Further work is necessary to improve the photovoltaic action. For this, we have to increase the thickness and material quality of the light absorbing layer, and improve the quality of junctions.&nbsp

The parameters of crystalline semiconductor such as types of semiconductor,uniformity of impurity concentration of doped wafer, majority charge carrierconcentration, sheet resistivity of doped wafer surface play an important rolein solar cell fabrication process during emitter diffusion, that is the mostcritical step. In this paper, we have used a low cost in house made hot probe measurement setup. A hot plate was used to heat up the wafer up to 100°C.Two k-type thermocouples were placed simultaneously in contact with thehot and cold surface of the wafer to measure the temperature in situ for bothhot and cold probe. We have used two copper probes with a voltmeterconnected to measure the potential difference (thermoelectric voltage)between two probes for various temperatures up to 100°C with an interval of10°C. We have taken measurement for commercial silicon wafer (thickness200 µm) and one side polished 4 inch diameter Si wafer (thickness 660 µm) todetermine the wafer type (n-type or p-type). We also calculated thermopower or Seebeck coefficient from the voltage vs. time curve, that is constantfor particular substrate. As a process monitoring tool for solar cell fabricationprocess, after n-type diffusion using POCl3 on p-type silicon wafer ofthickness 200 µm, we have done wafer mapping that gives us theinformation of doping uniformity over the whole surface of wafer both front and back side.

Temperature dependent majority charge carrier concentration and impurity concentration calculationsdone for p-type commercial (100) silicon wafer of thickness 200 µm where the wafer is heated by hot probeset up. By solving basic conductivity equation of semiconductor and Continuity & Poisson’s equationthermally generated carrier ∆p and Q are found respectively for the same temperature range 50°C-80°Cwith an interval of 10°C. For lower temperature ∆p and Q values are not exactly same but for highertemperature those values agree with conventional measurement.&nbsp

In this paper, modifying the spectral p-n junction model theoretical efficiencies have been calculated for a GaInP2/GaAs/Ge multijunction solar cell for AM1.5 global and AM1.5 direct normal under 1 sun condition. Base on these efficiencies, performance of this solar cell is analyzed. It has been seen that thinning the thickness of top cell, increases the efficiency. Increasing the bandgap and sun concentration would increase the efficiency. These theoretical efficiencies of GaInP2/GaAs/Ge multijunction solar cell have been achieved upto 38.16%% for AM1.5G, and 41.38% for AM1.5D under 1 sun condition respectively due to thinning the top cell thickness.

We have investigated the possibility of growing oriented crystalline silicon films, 2 to 3 micron thick, from silane-hydrogen mixture, by hot wire chemical vapour deposition (HWCVD). Several substrates i) amorphous SiO 2 , ii) oriented TiO 2 layer on glass, iii) textured nickel-5% tungsten metal strip, and iv) crystalline sapphire have been used in this work. The growth is performed in two stages; a) nucleation step using dilute mixture SiH 4 :H 2 in the ratio 1∶20 at 400°C, followed by b) thickening step at 540°C, in which SiH 4 :H 2 ratio is gradually enhanced to 8∶20. The nucleation step promotes directional growth and leads to (220) oriented thick layers. Several characterization techniques, scanning electron microscopy (SEM), x-ray diffraction (XRD) have been used for structural investigations such as preferred crystal orientation, grain size, grain shape and surface topography.

We report synthesis of highly (220) oriented and passivated polycrystalline silicon films on glass by using Hot Wire Chemical Vapor Deposition (HWCVD) without using any buffer. Oriented growth is initiated by deposition at 400°C using dilute mixture of Silane(SiH 4 ) and Hydrogen(H 2 ), a condition which favours growth of (220) oriented nuclei. After that most of the growth is done at 600–700°C using less dilute SiH 4 + H 2 . Films are passivated by in-situ soak in atomic hydrogen between 400–300°C. At 300K, films have dark conductivity about 10−6 (Ω-cm)−1. Illumination with a white light LED of flux about 1 sun increases the conductivity to 1−2x 10−5 (Ω-cm)−1. In addition photoluminescence emission is observed both at 18 K and at 300K. These features suggest films are well passivated.

We have investigated the possibility of growing silicon films, 2 to 3 micron thick, from silane-hydrogen mixture, by hot wire chemical vapour deposition (HWCVD). Several substrates i) oriented TiO2 layer on glass, ii) crystalline sapphire have been used in this work. The growth is performed in two stages; a) nucleation step using dilute mixture SiH4:H2 in the ratio 1:20 at 400 degC, followed by b) thickening step at 540 degC, in which SiH4:H2 ratio is gradually enhanced to 8:20. Transmission and reflection spectroscopy have been used for determining optical characteristics of the film.

Our study involves the cleaning, wet etching, and characterization of GaAs wafer in the firstsemiconductor device fabrication laboratory at the Institute of Electronics, Atomic EnergyResearch Establishment. Our primary step is to develop necessary photolithography skill andthoroughly characterize equipment needed to perform photolithography including Hot plate,Spinner, Mask Aligner. Here, our studies are extended to photo resist thicknessmeasurements using surface profiler and SEM to view etched surface quality. The experiences and the results of this study will benefit the students who are interested in thesemiconductor fabrication field in Bangladesh.&nbsp