Study On The Synthesis Of Gold Plasmonic Nanostructures And Their Applications In Polymer Solar Cells

Polymer solar cells have attracted extensive attention due to their advantages of being light weight,low cost,flexible and compatible with a solution-based roll-to-roll manufacturing and etc.However,compared to the traditional silicon based solar cells,the relatively low power conversion efficiency caused by the low light absorption in photoactive layer restricts their further development and practical applications.In view of the low carrier mobility and the short exciton diffusion length of the active layer composed of conjugated polymer donor and fullerene derivative acceptor,the optimum thickness of photoactive layer is < ~ 200 nm,which determined by a trade-off between maximizing the optical absorption and meanwhile minimizing the charge recombination loss for efficient charge extraction.Plasmonics has been developed into a promising technique to enhance the light harvesting of the photoactive layer in PSCs while without needing of enhancement in thickness by their local surface plamsmon reasonance(LSPR)effects and scattering effects.According to related research work,the ordinary method of adding the metal nanoparticles in the polymer solar cells is spin coating after mixing the metal nanoparticles into precursor solution of the functional layer.There’s a high risk of aggreation during the process of synthesis,purification,refusion and spin coating,which means an arduous work.The aggregation not only reduces the surface plasmon resonance effect,but also destroys the micromorphology of the active layer,which is harmful for the battery performance.Therefore,the aggregation of metal nanoparticles in the battery is a key problem to make full use of the surface plasmon resonance effect to improve the light absorption and photoelectric conversion efficiency of the solar cell.In addition,the location of plasma metal nanostructures in the battery also has significant influence on the enhancement of the optical absorption of active layer.It can avoid exciton recombination resulting from the direct contact with the active layer when the metal nanoparticles are placed on the buffer layer or electrode interface.However,the LSPR effect is concentrated in the near field of the surface,which is not conducive for the active layer to obtain enough light absorption.In this paper,three measures of optimizing plasmonic-enhanced polymer solar cells are proposed for the aggreation and locations of of particles in solar cells.(1)Based on ultrasonic,the preparation of size-controllable and multi-morphology gold nanoparticles on the surface of 2-D titanium oxide has greatly simplified the addition process in solar cells.The aggregation of metal nanoparticles has been solved,and the resonance absorption peaks have been widened.The average photoelectric conversion efficiency of solar cells based on P3 HT and PTB7 has been increased by 20.0% and 14.5%,respectively.(2)Based on the assembly and reaction ion etching technology,the aggregation of metal nanoparticles has been avoided and the particles are successfully extended into the active layer by the construct of Au/Ti O2 columnar array.The efficiency of soalr cells has been improved to a certain level and still has room for enhancement by optimizing dispersed density of nanoparticles and the hight of columnar structure.(3)Based on the vacuum thermal evaporation and heat treatment technology,the array with well-dispersion and size-controllable gold particles has been constructed on the surface of the Ti O2,which completely avoids aggregation.Combining with reactive ion etching technology,a simple construction method of Au/Ti O2 column array structure has been developed.In addition,silver and gold/silver alloy nanospheres can also be obtained by this method,which is possible for the study of optimizing the performance of polymer solar cells via adding different kinds of metal plasma nanostructures.To sum up,three simple ways of building gold plasma nanostructures have been developed in this paper to solve the problem of aggregation.The light absorption and efficiency of soalr cells has been greatly enhanced by the study of influence on the gold nanoparticles.The mechanism of improvement the performance by Au/Ti O2 array has been discussed.In view of the unique photoelectric characteristics of the noble metal-titanium oxide composite structure,the methods developed in this paper have potential applications in a variety of optoelectronic devices,such as other photovoltaic devices,water splitting,photocatalytic redox,etc.