Design,Synthesis Of Naphthalene Diimide-based Polymers And Their Applications In Polymer Solar Cells

Polymer solar cells（PSCs）have attracted significant interests due to their unique features including lightweight,flexibility,portability and solution processing accessible for large-area modules.Over the past decade,with the combined developments of material chemistry and device physics,the highest efficiency of single-junction PSCs reported have exceeded 13%.However,there are many problems to solve from laboratory research to industrial production.Thereby,the development of efficient and applicable materials is still vitally important to realize commercialization of PSCs.Herein,a series of novel functional polymers were developed and used in cathode interlayers（CILs）or active layers in PSCs.In chapter 2,we present a microwave-assisted one-pot three-component polymerization of alkynes,aldehydes and amines for the synthesis of new amino-functionalized polymers.The resulting polymers can be easily dissolved in alcohol and alter the work function of electrode and thus utilized as cathode interlayer for PSCs.It was found that these CIL materials can effectively elevate photovoltaic performance.Devices employing these polymers as the cathode interlayer achieved a high power conversion efficiency（PCE）of9.49%.These results suggest that multicomponent polymerization can be an effective strategy for the synthesis of functional polymers.In chapter 3,we introduce naphthalene diimide（NDI）as a build block in three-component polymerization（TCP）system and synthesize a series of NDI-based amino-functionalized polymers.The effects of chemical structure of amine groups on the resulting polymers‘electrode modification capability and self-doping behavior were explored by conducting scanning Kelvin probe microscopy and electron paramagnetic resonance（EPR）spectroscopy studies,respectively.It was found that the decreasing electron-rich property and enhancing steric hindrance of amine end groups can substantially influence the electrode modification capability and self-doping behavior of the resulting polymers.Likewise,these amino-functionalized polymers were also utilized as the cathode interlayer for PSCs.Device with PTB7-Th:PC₇₁BM as the photoactive layer exhibits a high PCE of 9.34%.These results may trigger broad research interests in developing effective multicomponent polymerization toward functional polymer materials.In chapter 4,we have designed and synthesized a series of NDI-based amino-functionalized polymers with different polymeric side groups and backbones and systematically study the influence of the chemical structure of amine groups on the properties of oxidation potential of side chains,charge carrier mobilities,self-doping behaviors,interfacial dipoles and trap passivation effect.Moreover,the introduction of rigid acetylene spacer on the backbone can substantially enhance the electron transporting property.When these polymers were used as CILs,high PCEs of 10.1%and 15.2%were respectively achieved in polymer and perovskite solar cells.Importantly,these newly developed n-type polymers were allowed to be processed over a broad thickness range of CILs in photovoltaic devices and a prominent PCE of over 8%can be achieved in polymer solar cells even when the thickness of CILwas over 100 nm.In chapter 5,we have designed and synthesized a series of naphthalenediimide-thiophene copolymers with symmetric or asymmetric alkyl side chains and examined the effects of asymmetric alkyl chain substitutions on polymer aggregation,crystallinity,morphology and charge transport of blend films.It was found that the asymmetric alkyl chain substitutions can effectively enhance the crystallinity and aggregation of the resulting polymers.Importantly,the improved aggregation and crystallinity could ensure the superior morphology and better charge transport properties.When these polymers were used as acceptor in all-polymer solar cells,a high PCE of 6.89%was obtained.