Insitu Preparation Of Inorganic Nanometer/Conjugated Polymers Thin Films And Study Of The Photovoltaic Properties

In the past two decades,organic solar cells have attracted much attention due to the wide range sources of raw materials,relatively low cost,simple preparation process,ease of structure modification and large scale manufacture.But it also has the problem that the exciton binding energy is large,the carrier mobility is low,the device operation stability is poor and so on.In order to solve the above problems,inorganic /organic hybrid solar cells,in which inorganic nanocrystalline materials with higher dielectric constant,better electron affinity and stability are used to instead of the fullerene electron acceptor in organic solar cells,were proposed.When assembling inorganic /organic hybrid solar cells using nanocrystallines fabricated by the colloidal synthesis,it is necessary to add surfactants to the surface of the inorganic nanocrystallines to control its morphology and properties,and need for the addition of co-solvent to mix the organic donor material and inorganic nanocrystalline material.However,the surfactant will impede the charge-carrier transport between the organic donor material and the inorganic nanocrystalline material,and the use of co-solvent will affect the tendency of organic donor polymer chains and the solubility of inorganic nanocrystals,and thereby affect the efficiency of the device.In situ preparation of inorganic / organic solar cell active layer,which is equivalent to in situ formation of inorganic polymer in the organic polymer system,achieved the effective combination of the polymer and inorganic semiconductor,and get rid of the influence of the surfactants and co-solvents.This paper was centered on in-situ fabrication of inorganic nanocomposite / conjugated polymer films and the study of their photovoltaic properties.On the basis of elaborating the advantages and research backgrounds of inorganic / organic hybrid solar cells,the inorganic / organic hybrid solar cells were prepared,and the main parameters and performance of the device were analyzed.Firstly,the precursor of CdS nanocrystal acceptor,cadmium complex of xanthate,was synthesized.The morphology,structure,optical,physical and chemical properties of the materials were characterized.Next,solar cell active layer was fabricated by in situ preparation of cadmium complex of xanthate and the classical polymer donor material: 3-hexylthiophene polymer（P3HT）or the excellent polymer donor materials in our laboratory: oly[5,10–di（2-（2-ethylhexyl）-3-hexylthiophen-5-yl）-benzo[1,2-b:4,5-b’]-dithieno[3,2-b]thiophene-alt-ben zo[c][1,2,5]thiadiazole]（PDTBDT-BT）and oly[5,10-di（2-（2-ethylhexyl）-3-hexylthiophen-5-yl）-benzo[1,2-b:4,5-b’]-dithieno[3,2-b]thiophene-alt-5,6-difluorobenzo[c][1,2,5]thiadiazole]（PDTBDT-FBT）the inorganic/organic hybrid solar cells were prepared,the main parameters and performance of the device were analyzed.Power conversion efficiency of 0.82% has been achieved in ITO/PFN/P3H:CdS/MoO3/Ag solar cells by optimizing the fabrication conditions.Secondly,the energy levels of CdS（conduction band and valence band）are at around-4.0 eV and-6.4 eV,respectively.The insertion of a CdS layer between the ITO cathode and the polymer active layer could provide a good energy level matching,which allows CdS to function well for electron collection and hole blocking.The absorption edge of CdS is located at about 516 nm,indicating that most of the visible light could pass though,which benefits in lowering the optical loss.On the other hand,the relatively high electron mobility of CdS（265 cm2 s-1 v-1）makes it a suitable material for cathode buffer layers to reduce the charge recombination.In addition,relative to CVD（chemical vapor deposition）and ALD（atomic layer deposition）,the method of thermally decomposition of cadmium xanthate complex is much more promising,because it can meet the economic and industrial requirements of mass production.Based on the above reasons,CdS thin film with different thickness were prepared by thermally decomposition of cadmium xanthate complex,and inverted organic solar cells（ITO / CdS / P3HT: PC61 BM / MoO3 / Ag）were fabricated using the CdS thin film as the electron transporting layer.The highest power conversion efficiency of 3.22% has been achieved by optimizing the fabrication conditions.Finally,we developed the method of thermally decomposition of cadmium xanthate complex into preparation of Sb₂S₃ and Bi₂S₃ thin films.Firstly,the precursor complexes of antimony and bismuth of xanthate were synthesized,and the structure and properties of the material were characterized.Then solar cell active layer was fabricated by in situ preparation of antimony or bismuth complex of xanthate and P3 HT.The inorganic / organic hybrid solar cells were prepared,and the main parameters and performance of the device were analyzed.