Studying the influence of angolas tropical climatic conditions on the operational efficiency of silicon photovoltaic solar cells and finding technological solutions to enhance their perfomance

MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MATEUS MANUEL NETO DISSERTATION TITLE: STUDYING THE INFLUENCE OF ANGOLA’S TROPICAL CLIMATIC CONDITIONS ON THE OPERATIONAL EFFICIENCY OF SILICON PHOTOVOLTAIC SOLAR CELLS AND FINDING TECHNOLOGICAL SOLUTIONS TO ENHANCE THEIR PERFORMANCE Major: Engineering Physics Code: 9520401 DISSERTATION FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN ENGINEERING PHYSICS SUPERVISOR: ASSOC PROF PhD NGUYEN NGOC TRUNG PROF PhD VO THACH SON HA NOI - 2018 CONTENTS CONTENTS i LIST OF SYMBOLS iv LIST OF ABBREVIATIONS vi LIST OF FIGURE viii LIST OF TABLES xii INTRODUCTION CHAPTER LITERATURE REVIEW 1.1 Overview of renewable energy use in the World 1.2 Overview of solar cell use in the Angola - 1.3 The photovoltaic effect 1.4 Physics of Solar Cells 11 1.5 Overview of Silicon Solar Cell Technologies -17 How does PERC technology improve performance? 20 1.6 Influence of tropical climate in the performance of PV panels 21 1.6.1 Spectrum -22 1.6.2 Irradiance 22 1.6.3 Module temperature 23 1.6.4 Wind speed 23 1.6.5 Incident angle 23 1.6.6 Effect of humidity on the solar panels -24 1.6.7 Effect of dust on the solar panels -25 CHAPTER THE INFLUENCE OF ANGOLA TROPICAL CLIMATIC CONDITION ON THE PV SYSTEM PERFORMANCE 27 2.1 Experimental introduction -27 2.2 Influence of Solar radiation 29 2.3 Influence of Temperature 32 2.4 Influence of humidity 37 2.5 Effect of radiation on PV characteristics 40 2.6 Effect of an inverter 42 2.7 Effect of wind actions on PV panels -42 2.7.1 General -42 i 2.7.2 Computational Fluid Dynamics (CFD) Procedure -47 2.7.3 Effect of wind actions on solar panels -51 Chapter summary 67 CHAPTER STUDY ON TITANIUM DIOXIDE APPLICATION AS SOLAR CELL SELF-CLEANING LAYER 68 3.1 Settlement overview of dust on a solar panels glass cover 68 3.2 Thin film TiO2 using as self cleaning material of solar panels 69 3.2.1 The self-cleaning properties -69 3.2.2 Theoretical basis of self-cleaning -69 3.2.2 1.Young’s equation -70 3.2.2.2 Cassie model 70 3.2.2.3 Wenzel model -71 3.2.2.4 Cassie and Baxter’s Equation -71 3.2.3 Thin film TiO2 using as self-cleaning material -72 3.3 Nanocrystalline TiO2 thin film deposited by spray pyrolysis technique and sol gel –hydrothermal method 73 3.3.1 Experiment details 74 3.3.2 Characterizing of TiO2pure and doped iron or tungsten thin film 77 3.3.2.2 Characterizing of Fe-dopedTiO2 thin film -81 3.3.2.3 Characterizing of W-dopedTiO2 thin films 85 3.3.3 Self-cleaning properties of TiO2pure and doped iron or tungsten thin film 88 Chapter conclusion -93 CHAPTER GROWTH AND CHARACTERIZATION OF Al2O3 ULTRATHIN FILM AS A PASSIVATION LAYER FOR SILICON SOLAR CELLS 95 4.1 The need for silicon solar cells passivation layer Al2O3 -95 4.2 Carrier Recombination in Crystalline Silicon -96 4.3 Surface passivation 98 4.4 Surface passivation materials 100 4.4.1 Silicon dioxide SiO2 101 4.4.2 Hydrogenated amorphous silicon nitride a-SiNx:H 101 4.4.3 Hydrogenated amorphous silicon a-Si:H 101 4.4.4 Aluminum oxide Al2O3 102 ii 4.5 Growth Al2O3 ultra-thin film by Atomic Layer Deposition - 102 4.5.1 Introduction ALD technique - 102 4.5.2 Growth process of thin film aluminum oxide by ALD 104 4.5.3 Process for p-type Si solar cells(PERC) fabricated - 105 4.5.4 The investigated method - 107 CONCLUSION - 117 The scientific and practical significance of the thesis - 118 Recommendations for Future Studies - 119 REFERENCES Error! Bookmark not defined iii LIST OF SYMBOLS Number Symbol Name A Quality factor C The specific heat capacity (J/K.kg) CF The force coefficient Cp The pressure coefficient D Average crystallite size E Energy e Electron EA Ionization energy EC Conduction band energy 10 EF Fermi energy 11 Eg Optical band gap energy 12 EV Valence band energy 13 F The force applied on the surface 14 ff fill factor 15 h Hole 16 J Current density 17 Jmax Current density at maximum power output 18 JSC Short circuit current density 19 m Mass (kg) of the material 20 Pmean 21 Q Quantity of heat (Joules) 22 R0 Initial resistance (Ω) 23 R Resistance between the contacts 24 RS Serial resistance 25 Rsh Shunt resistance 26 Rsheet Sheet resistance 27 t Time 28 T Transmittance 29 TA Absolute temperature 30 TC Calcined temperature The mean pressure iv 31 Te Environmental temperature 32 TS Substrate temperature 33 V Voltage 34 Vmax Voltage at maximum power output 35 VOC Open circuit voltage 36  Absorption coefficient 37  Thickness 38  Conversion efficiency of the solar cell 39 λ Wavelength 40 λex Excitation wavelength 41 e Electron mobility 42 p Hole mobility 43 ρ0 Initial resistivity (Ωm) 44  Resistivity 45 eff Effective lifetime 46 rad Carrier lifetime due to radioactive recombination 47 Auger Carrier lifetime due to band to band i.e Auger recombination 48 SRH Carrier lifetime due to defects i.e SRH recombination 49 Surf Carrier lifetime due to surface recombination v LIST OF ABBREVIATIONS Number Symbol Name AFM Atomic Force Microscope ALD Atom layer deposited APE Average photon energy CFD Computational fluid dynamics CVD Chemical vapour deposition DRE Department of Renewable Energy ECCP Energy Pool of Central Africa- EDX Energy Dispersive X-ray ETA Extremely thin absorber 10 FESEM 11 FTO 12 FWHM Full width at half maximum 13 IEA International Energy Agency 14 LED Light Emitting Diode 15 MB Methylene blue 16 MINEA Ministry of Energy and Water 17 MPPT maximum power point tracking 18 PV Photovoltaic 19 PCE power conversion efficiency 20 PDA Post deposition annealing 21 PECVD 22 PERC Passivized emitter and rear cell 23 PERL Passivized emitter and rear locally diffused cells 24 PMT Solar cells 25 PO Field Emission Scanning Electron Microscope Tin oxide doped Fluorine Plasmaenhanced chemical vapor deposition Power output vi 26 SHS Solar home system 27 SAPP Southern African Power Pool 28 SEM Scanning Electron Microscope 29 SPD Spray Pyolysis Deposition 30 STC Standard test conditions 31 TCO Transparent conducting oxide 32 TMA Trimethyl Aluminum 33 TTIP Titanium tetraisopropoxide 34 USPD Ultrasonic Spray Pyolysis Deposition 35 UV-VIS 36 VASE 37 XPS X-ray photoemission spectroscopy 38 XRD X-ray diffraction UV-VIS Spectrophotometer Variable-angle spectroscopic ellipsometer vii LIST OF FIGURE Figure 1.1 Price comparison of energy sources [5] Figure PV module price over time [14] Figure 1.3 Graph illustration absorption of a photon in a semiconductor with an Eg band gap [16] 10 Figure 1.4 Component parts of a typical PV cell 11 Figure 1.5 Graph illustration structure of a 1D p-n homogeneous solar cell 12 Figure 1.6 Ideal short-circuit current density of p-n junction solar cell as a function of Eg [22] 14 Figure 1.7 J- V curves of a solar cell in the dark and under illuminated condition [17] 15 Figure 1.8 Graph illustration equivalent circuit of a real solar cell [17] 15 Figure 1.9.Graph of p–n junction solar cell factor as a function of band gap 16 Figure 1.10 Market share of PV cells (%) [26] 17 Figure 1.11 Scheme of a modern crystalline silicon cell [29] 18 Figure 1.12 Imaging of Poly‐crystalline Si cell (a), and Mono-crystalline Si cell (b) [19] 20 Figure 1.13 The structure of a conventional cell (a) and the structure of a cell with PERC technology (b) [17] 20 Figure 1.14 A cell with PERC technology will generate more current due to the reflection of light at the backside of the cell 21 Figure Average monthly insolation levels in Luanda 27 Figure 2 Diagram of collecting and monitoring data of operating solar panels 28 Figure Kipp & Zonen’s Pyranometer Model CMP6, ISSO 9060 / WMO First Class Standard: (a) Solarimeters measurement system; (b) The anemometer 28 Figure The software for collect data 29 Figure The solar irradiance intensity through the experimental day in day 29 Figure Maximum output power versus solar radiation 30 Figure The PCE versus solar radiation 30 Figure The open circuit voltage Voc(a) and the short circuit current Isc (b) with varying solar radiation 31 Figure 2.9 The ambient temperature and modules temperature on time in day 33 Figure 2.10 Average panel temperature versus ambient temperature 34 Figure 2.11 Open circuit voltage (a) and Short circuit current (b) versus ambient temperatures 35 Figure 2.12 The conversion efficiency versus ambient temperature 37 Figure 2.13 Maximum power output versus wind speed 37 Figure 2.14 The relationship between open circuit voltage and relative humidity 38 Figure 15 The relationship between short circuit current and relative humidity 38 Figure 2.16 The relationship between relative humidity and ambient temperature 39 Figure 17 The relationship between relative humidity and PV efficiency 39 viii Figure 18 Equivalent circuit for amorphous solar cell The current sink I rec stands for recombination losses in i-layer 40 Figure 2.19 Current-Voltage characteristics of PV cells before and after projecting by neutrons with different illumination dose :1-=0; 2- =6*108; 3-=1.2*109; 4-=1.8*109; and 5-=2.4*109 41 Figure 2.20 Comparison of power converted by inverter (Pac) and power produced by PV system (Pmax) 42 Figure 21 Location of the application point of the global wind force acting on monopitch canopies (SR EN 1991-1-4/2006) 44 Figure 22 Scheme of a free standing panel in the air flow (a, c [81]); (b) the resulting movement due to flow separation [82] 44 Figure 23 Illustration of lift and draft forces 45 Figure 2.24 Wind speed (km/h) in Luanda shows days per month 46 Figure 25 Solar panels placed at ground level 47 Figure 2.26 Generated model of solar panels(a) Support and (b) Support with solar panels 48 Figure 2.27 Computational domain 49 Figure 2.28 Mesh of computational domain 49 Figure 2.29 Mesh of computational domain 50 Figure 30 Distribution of pressure and streamline of fluid flow around solar panels at centered XY plan – Wind velocity 3m/s & Attack angle 0o 51 Figure 31 Distribution of pressure and streamline of fluid flow around solar panels at centered YZ plan – Wind velocity 3m/s & Attack angle 0o 52 Figure 2.32 Distribution of pressure and streamline of fluid flow around solar panels at centered XZ plan – Wind velocity 3m/s & Attack angle 0o 53 Figure 2.33 Distribution of pressure on solar panels – Wind velocity 3m/s & Attack angle 0o 54 Figure 2.34 Effect of inclined angle of PV to aerodynamic characteristics - Wind velocity 3m/s & Attack angle 0o: a) Coefficient of lift and drag force and b) Aerodynamic quality 55 Figure 35 Distribution of pressure and streamline of fluid flow around solar panels at centered XY plan – Inclined angle 30o& Attack angle 0o 56 Figure 36 Distribution of pressure and streamline of fluid flow around solar panels at centered YZ plan – Inclined angle 30o& Attack angle 0o 57 Figure 37 Distribution of pressure and streamline of fluid flow around solar panels at centered XZ plan – Inclined angle 30o& Attack angle 0o 58 Figure 38 Distribution of pressure on solar panels – Inclined angle 30o& Attack angle 0o 59 Figure 39 Effect of inclined angle of PV to aerodynamic characteristics - Inclined angle 30o, Attack angle 0o: a) Coefficient of lift and drag force and b) Aerodynamic quality 60 Figure 40 Distribution of pressure and streamline of fluid flow around solar panels at centered XY plan – Wind velocity 9m/s & Inclined angle 30o 61 Figure 41 Distribution of pressure and streamline of fluid flow around solar panels at centered YZ plan – Wind velocity 9m/s & Inclined angle 30o 62 Figure 2.42 Distribution of pressure and streamline of fluid flow around solar panels at centered XZ plan – Wind velocity 9m/s & Inclined angle 30o 63 ix An increase in the growth rate was observed for increasing Tdep up to 200oC, whereas for Tdep> 200oC the growth rate was decreasing This can be explained by a lower reactivity of H2O at low substrate temperatures From a technological point of view, it is important to note that the purge times to remove H2O from the reactor increase drastically with decreasing Tdep Figure 4.12 and 4.13 plots the ALD Al2O3 films’ effective carrier lifetime and implied Voc measured by QSSPC (MODEL: SINTON WTC-120) as a function of Al2O3 film thickness It can see in Fig.5.10 that, the effective carrier lifetime was determined at an injection level in therange of x 1015 cm-3 The carrier lifetime of the ALD-Al2O3 films was about 210 µs for the sample with thickness about 4nm and non post-deposition annealing (PDA) The carrier lifetime of the ALD-Al2O3 films relative to that of the thickness With increasing thickness of Al2O3 films, the carrier lifetime was improved: from 210 µs to 580, 700 and 680µs at 6, 11, and 16 nm, respectively The ALD-Al2O3 films’ carrier lifetime was further improved by PDA The control sample’s carrier lifetime was increased from 210 to 300 µs after annealing For the thickness of 11nm, the carrier lifetime was increased to 770 µs after PDA For the thickness of 16nm, we obtained 730 µs of the lower value at 11nm 900 Effetive minority lifetime, (s) 750 600 450 300 Avg.Teffective Best.Teffective 150 10 12 14 16 Al2O3 film thickness, (nm) Figure 12 The plots effective carrier lifetime as a function of Al2O3 film thickness 660 Voc, (mV) 658 656 654 652 Avg.Voc Best.Voc 650 10 12 14 16 Al2O3 film thickness, (nm) Figure 13 The plots effective Voc as a function of Al2O3 film thickness 114 As seen in fig 4.13, the implied Voc also was increased dramatically, from 652.6 mV to about 656.9 mV with 4nm of thickness This result clearly showed the improved passivation performance of the ultrathin ALD-Al2O3 films The implied Voc was increased with increasing thickness, the value seems to saturate at about 658mV For 11nm of thickness, the maximum implied Voc, 659.1 mV, was obtained after PDA 20.8 20.7 20.6 cell, (%) 20.5 20.4 20.3 Avg.cell Best.cell 20.2 20.1 10 12 14 16 Al2O3 film thickness, (nm) Figure 14 The plots effective efficiency as a function of Al2O3 film thickness Figure 4.14 shows the plots effective efficiency as a function of Al2O3 film thickness It can see that, the efficiency is the best about 20.55% when the Al2O3 film thickness is about 11nm To activate the passivation performance, a series of post deposition annealing (PDA) at different temperatures for different thickness were carried out Effective minority lifetime, (s) 290 280 270 260 250 5nm 10nm 15nm 20nm 240 540 570 600 630 660 Annealing temperature, (oC) Figure 15 The plots effective Effective minority lifetime as a function of annealing temperature Fig 4.15 shows the effective minority carrier lifetime of p-type c-Si wafers passivated by 5, 10, 15 and 20 nm Al2O3 For original c-Si wafer, the eff was measured to be  ms After depositing a 20 nm-thick Al2O3 layers, a higher eff of  900 ms is obtained The results show that the effective minority carrier lifetime is improved when the Al2O3 thin films is deposited on c-Si surface To study the full potential and the thermal stability of the surface passivation 115 performances of Al2O3 layers, the lifetime samples were exposed to PDA at temperature (Ta) ranging from 530 to 670 oC with PDA time of in nitrogen enviromental The effective minority carrier lifetime increasing with increasing PDA of Al2O3 films and begin reduction at PDA about 600oC The effective minority carrier lifetime is maximium value about 288.3µs at PDA about 600oC and 20nm of thickness Al2O3 The different thickness of Al2O3 thin films, effective minority carrier lifetime was effected The blisters gas can be have before PDA,due to make reduction of effective minority carrier lifetime Morphology of Al2O3 thin films before PDA and after PDA illutration in figure 4.16 Figure 16 Morphology of Al2O3 thin films before PDA and after PDA Chapter summary In this Chapter, the Al2O3 ultra-thin films have been grown by ALD technique The ALD process offers highly conformal films with controlled thicknesses in the monolayer level The properties of aluminum oxide (Al2O3) films have shown excellent performances such as remarkable passivation behaviors on Si surfaces This study explores the conditions necessary for low temperature fabrication of Al2O3 thin films by the ALD technique The Al2O3 ultra-thin films have been grown by ALD technique Trimethyl aluminum (TMA) Al(CH3)3, and water have been used as the metal and oxygen precursors Thicknesses of the films were investigated depending on deposition cycles The estimated deposition growth rate was 1.0 Å/cycle at deposition temperature of about 200oC The Al2O3 ultra-thin films have refractive index n = 1.6 ÷ 1.75 in visible light The carrier lifetime depends on thickness of Al2O3 ultra-thin films The best valuable is about eff ~ 700 µs with thickness is about 11nm If used post-deposition annealing (PDA), the carrier lifetime iseff ~ 770 µs after PDA with thickness is about 11nm the efficiency is the best about 20.55% when the Al2O3film thickness is about 11nm.This result clearly showed the improved passivation performance of the ultrathin ALDAl2O3 films This study topics ranging from the fundamental mechanisms that govern the properties of nanolayer surface passivation schemes to the industrial feasibility of the technology For fabrication of Al2O3 one can use a cost-saving deposition technique called atomic layer deposition (ALD) The Al2O3 ultra-thin films can be used as a passivation layer to improve performance of Silicon based solar cells 116 CONCLUSION Experimented on the effects of climatic conditions in the Luanda, Angola on PV modules for a year was investigated The weather parameters were studied as the intensity of sunlight, ambient temperature, humidity and wind speed in outdoor conditions The investigation results show that: (i) Open circuit, short circuit current and performance of the c-Si solar cell system are linearly dependent on the illumination intensity (ii) As the ambient temperature rises, the temperature of the c-Si solar cell system increases, resulting in a reduction in the efficiency of the solar cell system Experimental results show that when the ambient temperature rises by about o, the temperature of the c-Si solar cell system increases by nearly 10o (iii) The humidity of the air also significantly influences the operation of the c-Si solar cell system Experimental results show that when the relative humidity of the environment increases from 60% to 85%, the efficiency of the PV decreases by 2.4% Humidity and wind also seemed to have an effect, but variations in humidity had a closely linked and relationship with temperature that makes it difficult to judge the true impact of humidity on performance The effect of wind as velocity, inclined angle, of solar panels to the solar cell system in Angola through the using the Computational Fluid Dynamic (CFD) software ANSYS Fluent was investigated The simulated results shown that: (i) The inclined angle of solar panels β = 30o within velocity of wind 9m/s and horizontal wind direction (attack angle α equal zero degree) is the best choice of system (ii) The lower left corner in the direction of the wind is the largest distortion of about 0.685 mm (iii) The equivalent stress is found maximum at vertical bar of support of solar panel The maximum value is about 7.46 × 104 Pa This value is lower than the limit stress of aluminum alloy (7.1 × 109 Pa) We have successfully deposited transparent TiO2 thin films using TiAcAc precursor by employing a simple and inexpensive spray pyrolysis technique The optical transmission spectra have a relatively high percentage of transmittance in the wavelength range from 400 to 900 nm The optical band gap is of the order of 3.32 ÷ 3.43 eV Fe doped- TiO2 thin film deposited by USPD: (i) Fe-doped TiO2 thin film formed anatase phase and tetragonal structure Crystal size is about 15 ÷ 25 nm (ii) Fe-doped TiO2 thin film have a relatively high percentage of transmittance in the wavelength range  = 400 ÷ 900 nm and optical band gap is Eg = 3.32 ÷ 3.43 eV (iii) Fe-doped TiO2 film have activity Photocatalytic on stain organic in visible light and the first-order reaction kinetics With 1.5% Fe-doped TiO2 sample have the best activity Photocatalytic with value kapp = 0.016 min-1 W-doped TiO2 thin film deposited by sol-gel mix hydrothermal method: (i) W-doped TiO2 thin film formed anatase phase and tetragonal structure Wolfram formed with structure WO3 117 (ii) W-doped TiO2 thin films have thickness about 1.30 ÷ 1.50 µm Crystal size is about 15 ÷ 25 nm High transmittance and optical band gap are about Eg = 3.6 ÷ 3.5 eV (iii) W-doped TiO2 thin films have activity Photocatalytic on stain organic in visible light and the first-order reaction kinetics With 2% W-doped TiO2 sample have the best activity Photocatalytic with value kapp = 0.14 min-1 Fe, W-doped TiO2 thin film have high transmittance and the good activity self-cleaning in visible light These samples can be applied for self-cleaning layer in thin film solar cells The Al2O3 ultra-thin films have been grown by ALD technique Trimethyl Aluminum (TMA) Al(CH3)3, and water have been used as the metal and oxygen precursors: (i) Thicknesses of the films were investigated depending on deposition cycles The estimated deposition growth rate was 1.0 Å/cycle at deposition temperature of about 200oC The Al2O3 ultra-thin films have refractive index n = 1.6 ÷ 1.75 in visible light (ii) The carrier lifetime depends on thickness of Al2O3 ultra-thin films The best valuable is about eff ~ 700 µs with thickness is about 11nm If used post-deposition annealing (PDA), the carrier lifetime is eff ~ 770 µs after PDA with thickness is about 11 nm the efficiency is the best about 20.55% when the Al2O3 film thickness is about 11 nm This result clearly showed the improved passivation performance of the ultrathin ALD- Al2O3 films The scientific and practical significance of the thesis We are analyzing the influence of Angolan tropical climate on performance of small scale, grid connected, silicon-based photovoltaic system located in Luanda, Angola By analyzing the effects of different variables that affected the performance of Silicon PV system located in an African tropical environment, it was observed that solar irradiance had the greatest impact on performance This implies that the unexpected factor such as dust accumulation will probably have a significant impact on the performance of the system by reducing the amount of sunlight that the PV panels are exposed to The calculated results using ANSYS Fluent software show that, inclination of panels has the largest effect on the wind loads acting on solar panels Small changes in panel inclination are observed to result in significant changes in wind loads We have successfully deposited transparent TiO2 thin films using TiAcAc precursor by employing a simple and inexpensive spray pyrolysis and sol-gel-hydrothermal techniques TiO2 composite films are essential for application as a self-cleaning surface in solar panels area, when transparency and low water contact angles are required Study and investigate the effect of ALD technology parameters on the formation of Al2O3 thin films applied as passive layer of c-Si solar cell: Study the conditions necessary for low temperature deposition of Al2O3 thin films by the ALD technique and examines properties of the resulting films This study topics ranging from the fundamental mechanisms that govern the properties of nanolayer surface passivation schemes to the industrial feasibility of the technology For fabrication of Al2O3, one can use a cost-saving deposition technique called atomic layer deposition (ALD) The Al2O3 ultra-thin films can be used as a passivation layer to improve performance of Silicon based solar cells 118 Recommendations for Future Studies Optimization studies on wind loads acting on the panels and the supporting structures in terms of solar panel inclination, spacing factor and length of panel as variable parameters is worthy to investigate Optimization of these parameters is attained through maximization of energy production from a solar farm depending on the latitude of the location on earth While the cost of the structural supporting system does not constitute the major cost compared to the cost of photovoltaic panels, the percentage of the cost due to the supporting system use and construction may be further reduced while still preserving the maximum energy output from that solar farm The study and understanding of Al2O3 surface passivation schemes in conjunction with the new ways of investigating, controlling and manipulating their properties, as outlined in this thesis, are important for the ongoing developments in the field of photovoltaic aiming at higher efficiencies and lower costs 119 THE LIST OF PUBLICATION 1) Mateus Manuel Neto, Pham Van Thang, Luu Thi Lan Anh, Pham Phi Hung, Nguyen Ngoc Trung and Vo Thach Son, Simulation investigation of wind effect on solar panels (Accepted in Journal of Science and Technology) 2) Mateus Manuel Neto, Luu Thi Lan Anh, Nguyen Trung Do, Nguyen Hoang Thoan, Nguyen Ngoc Trung, Chung Han Wu, and Vo Thach Son, Growth and characterization of Al2O3 ultra-thin film as a passivation layer for silicon solar cells., Journal of Science and Technology, Vols 126, 2018, pp 59-62 3) Luu Thi Lan Anh, Nguyen Thi Tuyet Mai, Mateus Manuel Neto, Ngoc Trung Nguyen, Ta Ngoc Dung, Trinh Xuan Anh, Phan Trung Nghia, Huynh Dang Chinh, and Vo Thach Son Effect of WO3 Doped TiO2 Nanoparticles for Solar Photocatalytic Degradation of Methyl Blue Asia worshop on polymer processing, 16-19/2017 Hanoi, Vietnam 4) Luu Thi Lan Anh, Nguyen Thi Tuyet Mai, Trinh Xuan Anh, Nguyen Kim Nga, Phan Trung Nghia, Ta Ngoc Dung, Huynh Dang Chinh, Mateus Manuel Neto and Vo Thach Son, Optimization of synthesized conditions of TiO2 photocatalysic nano particles using response surface methodology, Vietnam journal of Chemistry, Vol 53, issue 6e4 - 2015; pp 343-347 5) Lan Anh Luu Thi, Duc Hieu Nguyen, Mateus Manuel Neto, Ngoc Trung Nguyen and Thach Son Vo, Characterization of Nanocrystalline Titania Thin Film Deposited by Spray Pyrolysis Technique, Advanced Materials Research, Vols 875-877, 2014, pp 49-53 6) Mateus Manuel Neto, Luu Thi Lan Anh, Nguyen Duc Hieu, Pham Phi Hung, Nguyen Ngoc Trung, and Vo Thach Son The influence of tropical climate on the operation of a grid connected photovoltaic thin-film amorphous silicon system Kỷ yếu Hội nghị Những Tiến Vật lý Kỹ Thuật Ứng dụng, Tp Huế, 08-12 tháng 10 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