The basic structure of a crystalline silicon solar cell consists of a P-type silicon substrate, an n-type layer, an anti-reflection film (TiO2, SiO2 or Si3N4), a front silver electrode, a back aluminum electrode and a back silver electrode. The back-side silver electrode is an electrode formed by using silver conductive paste through screen printing and then sintering.
In the case of the same solid content, the different particle size, morphology, and ratio of silver powder would affect the viscosity performance. Tests show that the silver powder used in the back silver paste plays a key role in ensuring electrical performance, improving adhesion and welding power. In the case of low solid content, using a slurry prepared from micro-flaky silver powder, the resulting electrode film is dense and smooth, has excellent electrical properties, and good adhesion and welding properties.
The silver electrode paste on the light-receiving surface of solar cells uses high-performance metal conductive spherical silver powder.
The silver electronic paste used for the front electrode of silicon solar cell is mainly composed of three parts:
1. Superfine metallic silver powder with conductive effect. 70-80wt%. Ag powder has high photoelectric conversion efficiency.
2. Inorganic phase that plays a role of solidifying flux after heat treatment. 5-10wt%
3. The organic phase that acts as a binding agent at low temperatures. 15-20wt%
Ultra-fine silver powder is the main component of silver electronic paste, which ultimately forms the electrode of the conductive layer. Therefore, the particle size, shape, surface modification, specific surface area and tap density of silver powder have a greater impact on the performance of the slurry. The particle size of the silver powder used in the silver electronic paste is generally controlled within 0.2-3um, and the shape is spherical or quasi-spherical. If the particle size is too large, the viscosity and stability of the silver electronic paste will be significantly reduced, and because the gap between the particles is relatively large, the sintered electrode is not close enough, the contact resistance is significantly increased, and the mechanical properties of the electrode are also not ideal. If the particle size is too small, it is difficult to mix uniformly with other ingredients during the preparation of silver paste.
The silver coated copper powder materials prepared by Hongwu Nano’s technical engineers have relatively good sphericity, good dispersibility, uniform particle size, adjustable high tap density and superior electrical conductivity. The solar photovoltaic cell front electrode paste prepared by high-tap density silver powder has the characteristics of non-sticky rolls, easy printing, very small shrinkage, and dense sintered film, which fills the gap in the production of high-tap-density spherical silver powder in China.