Study On Silver Nanoparticles' Application In Heterojunction Solar Cells

In this paper,the surface plasmon characteristics of nano-sized silver particles prepared by a simple,safe and controllable solution reduction method,and its application in heterojunction solar cells were studied.Experimental results indicated that the silver particle plasmons deposited on the front electrode of the heterojunction solar cell show an excellent anti-reflection and simultaneous transmission-enhanced effect.In addition to discussion on the preparation process and growth mechanism of the nano-sized silver particles,the formation mechanism of the plasmons and the principle of the anti-reflection and transmission enhancement were involved.The main work and innovations are as follows:Starting from the mechanism of silver nanoparticle surface plasmon resonance,two types of silver nanoparticle surface plasmons,i.e.Localized Surface Plasmon(LSP)and Surface Plasmon Polariton(SPP)were introduced and their action mechanisms and applications were probed.In order to study the nucleation of nano-sized silver particles,we have explored the process and mechanism of the silver nanoparticle crystallization.During the reaction,the nano silver formed the nuclei first and then crystallized through the aggregation of the nuclei.The initially formed crystals acted as seed crystals,leading to the subsequent nuclei to form the corresponding crystals.The effects of the main factors such as reducing agent,pH value and post annealing on the Ag morphology and the characteristic of the obtained silver particle plasmon were studied experimentally.The nano-sized silver particles were prepared by using anhydrous ethanol and trisodium citrate as reducing agents respectively.It was found that nano-sized silver particles prepared by the latter method had a better effect to reduce the reflection and increase the transmission.The main mechanism is that the product of latter reaction is nano-sized silver sol with the absence of centrifugation process.So the content of silver nanoparticles was more than that in the former one,which is more conducive to the formation of surface plasmon.The pH value of the solution was adjusted by controlling the molar ratio of trisodium citrate and silver nitrate.It was found that the weak acid solution is more beneficial to form the Ag plasmons with excellent anti-reflection and enhanced transmission effect.In particular,the effect of the spinning times of nano-sized silver sol on the surface of the transparent conductive AZO films,the annealing temperature and time was investigated in detail.The annealing temperature significantly influences the surface morphology of nano-sized silver particles.In the annealing temperature range of 100-250 oC,the optimized temperature for better anti-refection and transmission enhancement are the temperatures of 150 oC and 200 oC.The Ag particles obtained at the annealing temperature of 200 °C were smaller and more uniform than that at 150 oC.Consequently,their nano-sized silver plasmons' anti-reflectance and transmission enhancement is more pronounced.Compared with the case of the bare AZO,the as-formed Ag/AZO structure can realize the ~18% reduction in light reflection on the surface and ~40% enhancement in transmission,which are much pronounced than that reported in literatures.