Study On The Performance Of Polymer Solar Cells With Ti-oxo Cluster-Based Cathode Interface Layer

Owing to the characteristics such as light weight,semitransparent,roll-to-roll flexible fabrication,organic solar cells（OSC）shows great potential in wide application scenary,which uses organic semiconductors as light-absorbing materials.The organic solar cells device is usually composed of active light-absorbing layer,interlayer and electrode.The interlayer,including cathode interlayer and anode interlayer according to the relative polarity of the electrode,is located between the active layer and electrode.The interlayer plays an essential role in determining the carrier transport behavior to improve the overall device performance of organic photovoltaics.Thereinto,the cathode interlayer for electron transport should be capable of effectively reducing the cathode work function,of high electron mobility and conductivity,readily into good film and efficient in charge extraction.As a result,we developed a series of novel cathode interlayer materials based on cyclic Ti-oxo cluster（CTOC）and successfully applied it into high efficiency polymer solar cells.The main contents of this thesis are as follows:The first chapter summarized the development history,device structure,working mechanism,performance parameters and the innovation of active materials in organic solar cells.In particular,the research of interlayer materials in OSC is introduced.Finally,the ideas and research contents of this paper are proposed.In the second chapter,an organic-inorganic hybrid electrolyte CTOC-N-Br was developed with easy synthesis and low cost,based on a cylic Ti-oxo cluster as inorganic core and naphthalene based organic ammonium bromide salts as electrolyte.The new hybrid electrolyte CTOC-N-Br exhibits excellent solubility in methanol.From the results of ultraviolet photoelectron spectrum,the work function of silver electrode can be effectively reduced.The characterization of electron spin resonance showed that the material exhibits obvious electron self-doping effect,which is favourable for electron extraction and transport.Grazing-incident wide-angle X-ray scattering and atomic force microscopy are conducted to obtain the desirable film morphology of CTOC-N-Br with amorphous state.As an univerisal cathode interlayer in non-fullerene and fullerene polymer solar cells,which delivers impressive power conversion effieiency of 17.19%（PM6:BTP-4Cl）,12.91%（PM6:IT-4F）,8.92%(PM6:PC₇₁BM)and 8.87%(PTB7-Th-PC₇₁BM).In the third chapter,a series of phenyl-functionalized CTOC named CTOC-CH₃,CTOC-H and CTOC-CF₃were synthesized via ligand exchange reaction of CTOC with 4-methylbenzoic acid,benzoic acid,4-trifluoromethylbenzoic acid.The PSC devices based on PM6:BTP-4Cl with CTOC-CH₃,CTOC-H and CTOC-CF₃as cathode interlayer give power conversion effieiencies of 17.08%,17.02%and 15.87%,respectively.It was found that phenyl-functionalized CTOC materials can form interface dipole so as to reduce the the work function of silver electrode through the ultraviolet photoelectron spectrum.Also,the characterization of electron spin resonance showed higher n-doping effect between the CIL materials and non-fullerene acceptor.On the other hand,the crystallinity of these materials can be reduced by adding 10%polyethylene glycol into the alcohol solution of CTOC-CH₃,CTOC-H and CTOC-CF₃.Benefiting from the improvement of CIL film morphology,the power conversion efficiencies of CTOC-CH3,CTOC-H and CTOC-CF3 devices are further increased to 17.26%,17.23%and 16.77%,respectively.