| Heterojunction batteries combine the advantages of crystalline silicon batteries and thin-film batteries.They exhibit excellent absorption performance similar to conventional crystalline silicon batteries and possess excellent passivation characteristics similar to thin-film amorphous silicon.These batteries have high potential for photoelectric conversion efficiency,higher double-sided ratio,effective reduction of heat loss,lower light attenuation,and a simple preparation process.Consequently,they are one of the most promising areas for investment in next-generation solar cells.This paper investigates the technology of preparing a reliable and usable heterojunction low temperature cured silver paste for electrodes.The study focuses on improving the conductivity,printability,and sintering properties of the cured silver paste for better application performance in heterojunction electrodes.(1)Silver-ammonia solution was prepared from silver nitrate with ammonia and ethylenediamine.Silver powder was prepared by controlling the concentration of reducing agent,reaction temperature and PH value of the system.The optimum reaction conditions were determined as follows:silver nitrate concentration 0.6 mol/L,ratio of ammonia to ethylenediamine 4:2,concentration of reducing agent 0.3 mol/L,initial temperature of silver-ammonia solution and reductant solution 10℃,pH value 1 1.56 and 5.83,respectively.A spherical silver powder with high dispersivity and uniformity was prepared by adding different types and amounts of dispersants.The results of the particle size distribution and compacting density analysis indicate that the silver powder,which was prepared using sodium hexametaphosphate and sodium dodecyl sulfate as dispersants,has excellent dispersivity and high compacting density,making it suitable for use in conductive silver paste.On the other hand,silver powder prepared with polyvinylpyrrolidone,polyethylene glycol,and sodium sulfate as dispersants has a narrow particle size distribution and a large average particle size,making it ideal for the production of sheet silver powder through ball milling.(2)This study utilized a spherical silver powder prepared via liquid reduction as the precursor for flaky silver powder.A ball mill was used with ethylene glycol and water as the medium,and the effects of ball milling time and precursor of silver powder on various characteristics of the resulting silver powder were investigated.XRD analysis indicated that while ball milling did not destroy the face-centered cubic structure of silver powder,it did decrease its crystallization degree and resulted in a preferred orientation of the(200)crystal surface.SEM analysis showed that longer milling times led to higher flake shapes in the silver powder.Over time,the overlapping of silver powder particles can lead to a decrease in performance.It has been found that the optimal milling time is 14 hours.Furthermore,the properties of flaked silver powder can vary depending on the precursor used.Precursors with larger sizes tend to result in lower compacting density.Additionally,preparing silver powder with a smaller diameter-thickness ratio can lead to a wider range of size distribution and poorer uniformity.(3)This study aimed to prepare a conductive phase of silver powder with a spherical shape using liquid reduction and ball milling methods.The resulting silver paste with low-temperature curing was then used for heterojunction batteries.The paste was prepared using an organic phase and a 13.05:86.95 mass ratio of organic phase to conductive phase.The study discussed the fineness,rheology,conductivity,and printing performance of the silver paste.The results indicated that using sodium hexametaphosphate as a dispersant in the silver powder resulted in a paste with low square resistance,small thixotropy,moderate viscosity,even printing lines,and high application value. |
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