Research On Multicrystalline Silicon Texturization Using Ultrasonic Standing Wave

Today, energy issues are paid more and more attention. As it is a branch of clean andrenewable energy, the development of solar energy is put more and more emphasis on bymany countries. According to the forecast of Joint Research Centre, solar energy will occupyan important strategic position in the future’s energy structure. The conversion efficiency isthe key issue of photovoltaic solar cells. In order to achieve a uniform and betterlight-trapping textured micro surface for improving the conversion efficiency, this paperstudies a new texturing method by using ultrasonic standing wave. The ultrasonic wave formsan ultrasonic standing wave by a reflecting end, and two ultrasonic standing wavesperpendicular to each other form a two-dimensional ultrasonic standing wave. The ultrasonicstanding wave controls reaction particles in acid solution to texture the multicrystalline silicon(Mc-Si). This paper applies orthogonal ultrasonic standing waves to Mc-Si surface texturingto searching a new way for achieving light-trapping structure.At first, this paper discusses the forces on a particle in the ultrasonic standing wave,establishes the equation of particle motion and analyzes particle movement. Two-dimensionalequation of particle motion is established by expanding the one-dimensional situation, andparticle movement is also analyzed. Then using MATLAB to simulate the particle movement,as a result, factors which act towards the movement and how they work are acquired. At last,experiments of particles controlling and tests of acid etching by ultrasonic standing wave arecarried on, and the conclusions are as follows:1. The fluidic particle in ultrasonic standing wave subjects to acoustic radiation force,viscous resistance force and virtual mass force. Through the combined effects of forces above,the particles form to lines parallel to each other in one-dimensional standing wave andgrid-like pattern in two-dimensional standing wave.2. By simulating particles movements and analyzing factors on it, it reveals that ultrasonicfrequency, amplitude of acoustic pressure and particle radius both have effects on theirmovements. Ultrasonic frequency affects the position of particles arrangement. Bothultrasonic frequency and amplitude of acoustic pressure affect the time of particlesmovements and their self vibrations. Particle radius affects the low frequency vibration ofparticles around the equilibrium position.3. The results of acid etching tests by using ultrasonic standing wave reveal that when ultrasonic standing wave added, Mc-Si can get more uniform micro surface, more deepcorrosion pits and better light-trapping effect.