Search

In this paper, silicon nanowires formation on N-type crystalline silicon wafer is studied. Metal-assisted chemical etching (MACE) technique is used in this study because it’s low cost but can produce a high-aspect-ratio of silicon nanowires. High-aspect-ratio silicon nanostructures have been proved as an effective texture for light trapping on silicon solar cells surfaces. The photons from incident light can be trap on the silicon nanowires and then being absorb into the cells which resulting high efficiency silicon solar cells. Traditionally, MACE works by creating a holes using metal catalyst such as Ag or Au in order to reduce of the etchant. The hydrofluoric acid (HF) and hydrogen peroxide (H 2 O 2 ) are function to etched the metal native oxide thus create a pores or nanowires formation. Roughness parameters of silicon nanowires was investigate in order to see the texture of silicon nanowires is rough enough to trap more photons on silicon wafer surfaces. Hence, roughness parameters are very important for texturing silicon wafer surfaces. In this study, root mean square (RMS) is used as an indicators for which acquired from the line profiles. Results from the roughness parameters shown a good compatibility.

Silicon nanostructures are one of the candidates for tomorrow technologies due to its novel physical properties. High-aspect-ratio silicon nanostructures have been proved as effective microstructures for enhance silicon solar cells efficiency. Silicon nanowires enhance solar cells efficiency by formation vertical well aligned nanowires on the top surfaces which give effects to the optical, electronic and physical properties of silicon solar cells. Silicon nanowires also can enhance the carrier collection of photovoltaic devices. There are two types of methods used to fabricate silicon nanowires such as top-down or bottom-up fabrication. One of the techniques to get high-aspect-ratio nanostructures is by using metal-assisted chemical etching (MACE). Metal-assisted chemical etching (MACE) technique has been adopted in many research experiments and technology due to its low cost fabrication of silicon nanowires but can form a high-aspect-ratio of silicon nanowires. MACE has demonstrates outstanding results of silicon nanowires in improving many microelectronics and photonic devices. Traditionally, MACE is operated by making a holes using metal catalyst in order to reduce of using the etchant. The mobility of the reactants impeded when the height of silicon nanowires increases which resulting insufficient holes. However, MACE also has advantages and drawbacks which appear such as long-vertical-well aligned silicon nanowires and some broken silicon nanowires due to very thin silicon nanowires which easily to break, respectively. In this paper, different solutions concentration is study using a two-step MACE process. The chemical solution contains HF/AgNO 3 and also H 2 O 2 . The experiment is conducted at room temperature. During the etching process, anisotropic growth different silver particles which used for the formation of the silicon nanowires on silicon wafer surfaces. As a results, the etch rate gives the effect on the silicon nanowires length. A comparative study of etch rate has been conducted in order to see clearly the differences.

In this paper, results of optical absorption of Pulsed Nd:YAG laser texturing on silicon solar cells surfaces, before and after post treatment were investigated. Silicon is known as a semiconductor which absorbs light poorly. This is because silicon material has indirect energy bandgap about 1.12 eV at room temperature which limits the efficiency of solar cells. Due to the material price, the thin silicon wafer solar cells are used to fabricate solar cells. Thin silicon solar cells is inexpensive and can perform better by improved the technique on fabrication of solar cells. One of the technique to improve solar cells efficiency for thin silicon wafer is a light trapping. Thin silicon wafer come with disadvantages which is cannot absorb longer wavelength. Therefore, to improve light trapping on thin silicon solar cells, a good textured must be created on the top of the silicon wafer surface in order to prolong the light path refractive and reflective inside the solar cells. This paper shown Pulsed Nd:YAG laser is used for making parallel pattern and grid pattern as a textured on silicon wafer top surfaces. After laser texturing is completed, the samples were then immersed in KOH solution. KOH solution is used to removed the unwanted particles and clean the silicon surfaces. An expected result of this investigation is that the optical absorption for both after post treatment Grid pattern and Parallel pattern exhibit high absorption, compared to the sample of Grid pattern and Parallel pattern non-post treatment which have low absorptions. The higher value of absorption for laser texturing on silicon wafer is start from 380 nm until 880 nm. The absorption decrease a little bit from 880 nm until 1050 nm. Interestingly, the silicon wafer with laser textured still have absorption for infrared light from 1050 nm until 1200 nm. This results means, laser texturing with post treatment can improved light absorption of thin silicon wafer which is trap more photons thus will resulting high efficiency.

Surface texturing is very important in silicon solar cells fabrication in order to enhance light trapping by reducing surface reflectance. Basically, silicon solar cells surfaces will be etched by chemical solution either anisotropic etched or isotropic etched which are known as conventional methods. The chemicals that have been used for this conventional method includes alcohol, acids, potassium hydroxide and addictive chemical like surfactant. Even though the texture surfaces created by chemical etched can reduce the reflectance, this technique is not environmental friendly. This technique could only be applied on monocrystalline silicon, but not for the multicrystalline silicon because of the presence of high selectivity of etching along specific directions and multiple crystallographic grain orientation. Moreover, the chemicals waste could harmed and give pollution to the environment. In this paper, new technique has been used to texture the silicon solar cells surfaces. The new texturing technique proposed in this paper is pulsed Nd:YAG laser. By using pulsed Nd:YAG laser, it can texture silicon solar cells surfaces and reduce the reflectance. Pulsed Nd:YAG laser also can working independently on any types of silicon surfaces. However, the groove lines of laser texturing depending on X-Y translation table that connected to pulsed Nd:YAG laser system. This paper explained the effect of various X-Y translation table settings of pulsed Nd:YAG laser to texturing silicon solar cells surfaces in order to reduce the reflectance percentage. As a result, pulsed Nd:YAG laser texturing on silicon solar cells surfaces in this paper shown the reflectance below than 5% which is very significant in order to increase absorption of incident solar radiation.

This paper presents the performance between silicon germanium (SiGe) and crystalline germanium (Ge) solar cells in terms of their simulated open circuit voltage, short circuit current density, fill factor and efficiency. The PC1D solar cell modeling software has been used to simulate and analyze the performance for both solar cells, and the total thickness is limited to 1μm of both SiGe and Ge solar cells. The Si0.1Ge0.9 thickness is varied from 10nm to 100nm to examine the effect of Si0.1Ge0.9 thickness on SiGe solar cell. The result of simulation exhibits the SiGe solar cell give a better performance compared to Ge solar cell. The efficiency of 9.74% (VOC = 0.48V, JSC = 27.86mA/cm2, FF =0.73) is achieved with Si0.1Ge0.9 layer of 0.1μm in thickness whilst 2.73% (VOC = 0.20V, JSC = 27.31mA/cm2, FF =0.50) efficiency is obtained from Ge solar cell.

Monocrystalline silicon texturization will be elaborate in this paper as a new method for texturing silicon surface. Normally, silicon surface will textured by using wet chemical etched. Some of crystalline wafer is ineffective when using conventional methods, because the different crystallographic orientation of regions of diversified consequence. Conventional method which is wet chemical etched always shown not uniform texture. So, the texturization with laser will introduce as a promising method in reducing reflection on silicon surface. This is the reason for conducting this research. Field Emission Scanning Electron Microscopy (FESEM) and digital microscope are performed to evaluate the results. Texturization of monocrystalline silicon surface by using Pulsed Laser Nd:YAG was found to be promising method in terms to avoid chemical texturing etched method. Compared to the conventional texturing method, laser texturization is much more independent on grains crystallographic orientation. Higher homogeneity texture can be reached when using laser Nd:YAG compared with chemical or electrochemical methods. The heat affected area caused by material damages is related with presented method limitation implementation practically. However, one step of chemical etching will be used to remove the damages after laser texturization. The main reason conducted this new methods are to reduce reflectance from bare or polished silicon surface and adapt it into solar cell manufacturing process. This new methods are expected to gives high efficiency solar cells.