The Application Of Nanoparticles Based On Noble Metal Elements In Quantum Dots Solar Cells

Solar cells based on colloidal quantum dots(CQDs)have progressed quickly in recent years,especially lead chalcohgenide(Pb X,X=S,Se,Te)CQDs,due to their attractive advantages.For example,the strong quantum confinement effect makes the bandgap of Pb S CQDs tunable in the near-infrared region(NIR)which is favorable to the NIR light absorption of solar cells.In addition,the low-cost solution process of CQDs solar cells is convenient for large-scale manufacturing.Based on the investigation over the past decades,the certified record power conversion efficiency(PCE)of CQDs solar cells has reached 12.0 %.However,the PCEs of the current CQDs solar cells are still far away from their theoretical efficiency(45 %),largely due to the huge number of surface trap states that lead to poor charge–carrier lifetime and short diffusion lengths.This limits the thickness of active layer as well as the light absorption of solar cells.To solve this problem,the surface plasmon resonance effect of noble metal nanoparticles(NPs)provides an effective way to overcome the limitation of light absorption in photovoltaic devices via far-field scattering effect,near-field enhancement induced by localized surface plasmon resonance(LSPR),and plasmonic hot-electron transfer.Based on this theory,this thesis explored the application of noble metal NPs with different shapes in Pb S CQDs solar cells.Moreover,we also investigated a nontoxic ternary QD which is based on noble metal elements.And its optoelectronic properties as well as application in devices were studied.The main content is listed as follows:Chapter 1: The introduction of noble metal NPs and work mechanism of solar cells are outlined.The basic properties and background of quantum dots and the application of noble metal NPs and QDs based on noble metal element in solar cells are introduced.Chapter 2: The synthesis and surface modification of gold nanobipyramids(Au BPs)and nanospheres(NSs)were studied.We analyzed the photophysical properties and morphology of Au BPs and Au NSs with/without mesoporous silica layer.Besides,four different size of Au BPs were synthesized for further investigation.Chapter 3: The performance and work mechanisms of devices based on Au BPs or Au NSs are discussed and the best PCEs were achieved via optimizing the position,concentration and thickness of mesoporous silica layer of noble metal NPs.Utilizing the complementary position of scattering peaks,Au BPs and Au NSs were mixed together to realize the broadband enhancement of light absorption,reaching the PCE of 9.58 %.Chapter 4: The nontoxic Ag Bi S2 QDs is based on noble metal element.We investigated the optoelectronic properties of Ag Bi S2 QDs and three different device structures based on Ag Bi S2 QDs.Firstly,we optimized the performance of solar cells with Ag Bi S2 and Pb S QDs heterjunction structure and achieved a PCE of 3.22 %.Secondly,the environmentally friendly solar cells of pure Ag Bi S2 QDs were fabricated using tetramethylammonium iodide(TMAI)and 1,2-ethanedithiol(EDT)as ligands,having a PCE of 0.65 %.Finally,we explored Ag Bi S2 QDs and polymer hybrid solar cells,and a PCE of 2.05 % was achieved via using PBDTBDD-T as hole transport layer.In conclusion,with the theory of CQDs solar cells as the foundation,this dissertation investigated the synthesis of noble metal NPs and nontoxic Ag Bi S2 QDs as well as their application in solar cells.