The Preparation And Performance Study Of Low~temperature Curing Silver Paste For Grid Electrode Of TFSC

Thin film solar cells(TFSC)are important developing direction of clean energy.The preparation of the TFSC grid electrode is one of key factors for the high efficiency application of the TFSC.The fabrication of the high-performance low temperature curing silver paste used for the TFSC grid electrode which is prepared by screenprinting has broad prospects for application.Low temperature curing silver paste of TFSC grid electrode has to have some critical characteristics of high conductivity,high aspect ratio and anti-aging properties.In order to prepare the high-performance low temperature curing silver paste used for the TFSC grid electrode,this paper focused on how to improve the conductive properties of the cured film of the silver paste,increase the aspect ratio and improve the aging resistance.The conclusions are as follows.In order to improve the conductivity of the cured film by using the size effect of the nanomaterials,the silver nanomaterials(silver nanoparticles and silver nanowires)prepared in the laboratory were used as the conductive filling phase.Silver nanoparticles with controllable size were fabricated by chemical reduction method,and the nanoparticles size was influenced by the reaction process parameters(reaction temperature and time),raw material mixing ratio and concentration(PVP molecular weight and silver nitrate concentration).The high purity silver nanoparticles were obtained by high-speed centrifugal method after dilution in the ethanol.Silver nanowires with different sizes were also prepared by the same chemical reduction with different the reaction process parameters(reaction temperature and time),in which different kinds of nucleating agent were added into the raw material.The high purity silver nanowires were obtained by filtering under normal pressure after dilution in the ethanol.The conductivity of the silver paste cured film was improved by controlling the additon of silver powders and the proportion of mixed silver powder,silver nano-materials.The mixed silver powder comprises high diameter-thickness ratio flaky silver powder and low diameter-thickness ratio spherical-like silver powder,which could improve the conductivity of the cured film and the printing properties of the silver paste.The addition of silver nanoparticles with the diameter of 30~50nm and nanowires with the diameter of 30~60nm and different aspect ratio had improved the conductivity of the cured film obviously.The rheological properties and printing properties of the silver paste were investigated and the relationship between them was also discussed.The influence of silver content on the rheological properties of silver paste such as viscosity,thixotropy,yield stress,elastic modulus and loss modulus was explored.In this paper,the cured film was subjected to heat aging,ultraviolet aging,high temperature aging and other aging tests.The effects of aging on the electrical conductivity,adhesion,color change and microstructure of the cured film were studied.