The Application Of Glod Nanoparticles,Silicon Oxide,Graphene And Their Composite Materials In PTB7:PC₇₁BM Polymer Solar Cells

Polymer solar cells(PSCs)have attracted widespread attention due to their excellent characteristics,such as low product cost,good mechanical flexibility,simple preparation process and suitable for mass production.So far,power conversion efficiency(PCE)of PSCs has not reached the threshold for commercial applications.The photoabsorption of active layer,effective dissociation of excitons,and the transport and collection of free carriers are significant factors affecting the efficiency of PSCs.Recent researches are mainly concentrating on photonic crystals,antireflection coatings and surface plasmon nanostructures to improve the light absorption.The local surface plasmon resonance(LSPR)effect can create strong near-field electromagnetic fields to improve the light absorption of surrounding materials.The surface plasmon structures used for light trapping can be divided into two categories:nano gratings and nanoparticles.This thesis mainly focuses on PTB7:PC7iBM solar cell system.Here,we doped active layer and electron transport layer with Au nanoparticles(NPs),nano silica and its composite materials,graphene and graphene quantum dot to improve the photoelectric conversion efficiency.The main research contents are as follows:1.Au NPs exhibit LSPR effect,which helps improving absorption efficiency of light under the condition of not increasing the thickness of active layer.Here,we prepared several Au NPs with different particle sizes,and then doped them into the photovoltaic devices.It is found that the photocurrent density can be improved obviously by Au NPs.Addition of 50 nm Au NPs in ZnO ETL resulted in 10%efficiency enhancement from 3.20%to 3.52%.2.The study has shown that silica NPs embedded in polymer solar cells can induce subsequent internal reflection,which leads to increase the optical path length and helps to the light absorption of active layer.SiO2@Au,Au@SiO2 core shell composite NPs have the advantages of both SiO2 and Au NPs,Here,we prepared these nanomaterials,and then doped them into active layer or ZnO transport layer of inverted PSCs.The results show that SiO2 NPs and its composite NPs can greatly enhance optical absorption and PCE.Addition of SiO2@Au and Au@SiO2 core-shell NPs to ZnO ETL led to a more remarkable efficiency enhancement,reaching 4.33%and 3.99%,respectively.3.Graphene(RGO)has advantages of high optical transmittance,low resistance,adjustable work function and stable physical and chemical properties.Graphene quantum dots(GQDs)have unique optical properties and excellent electronic conductivity.GQDs can effectively prolong the lifetime of carriers and increase the quantum yield.In this thesis,RGO solution was prepared by ultrasonic method,and GQDs were prepared by one-step hydrothermal reaction which used graphene oxide slurry as raw material.The particle size of GQDs is 8?10nm.The prepared RGO and GQDs were embedded into the active layer or the electron transport layerand it is found that the photocurrent of the device is greatly improved.