Synthesis,Properties And Application Of Functionalized Amphiphilic Fullerene Derivative Interface Materials

With the advantages of light weight,low cost,and possibility to prepare flexible device,the polymer/organic solar cell（PSCs）had a core layer of organic semiconductor material.The approach of introducing functionalized fullerene derivatives and conjugated polyelectrolyte layer on the cathode interface engineering was always an important way to obtain high efficiency device.Research works of this are mainly focused on the synthesis of functionalized amphipathic fullerene derivatives,the measurement of their self-organizing behavior and the application in inverted PSCs.On cathode interface control,a series of functionalized fullerence derivatives with polar groups of ether chain,amine,quaternary ammonium salt and sulfonatewere were synthesized and applied as cathode interface materials in inverted PSCs.The introduction of functionalized fullerence derivatives could improve the interface compatibility between the active layer and inorganic buffer layer and reduce the interface barrier effectively,those results were beneficial for the enhancement of power convention efficiency（PCE）.The concrete research contents are as follows:（1）The fullerene block and fluorene block were used to synthesize a series of functionalized amphiphilic fullerene derivative,and four diblock fullerene derivatives named C₆₀-2BEFPE,C₆₀-2DPE,C₆₀-4HTPB and C₆₀-PHFBS with different polar groups（ether chain,amine group,quaternary ammonium salt and sulfonate）on the side chain of the fluorene structure were designed and synthesized.By control the length of conjugated main chain,two sub-triblock fullerene derivatives named C₆₀-2TEBPE and C₆₀-4TPB were designed and synthesized.Finally,three triblock fullerene derivatives named C₆₀-PEHBS,C₆₀-2HMTPB and C₆₀-2EHTPB were also synthesized by altering the position of the differene polar groups on the side chains of fluorene block.Accoeding to the UV absorption spectra,it was found that the functionalized fullerene derivatives with same conjugated main chains also had similar UV absorption spectra.For the fullerne derivatives with same polar groups on side chains of fluorene block,the UV absorption peak appeared a certainly red shift with the increasing number of conjugated structures in main chain.（2）The film formation of three kinds of fullerene derivatives on the surface of zinc oxide（ZnO）were researched by atomic force microscopy and the effect of various fullerene derivatives on the enhancement of ZnO energy level were also studied by ultraviolet photoelectron spectroscopy（UPS）.It has been found that different fullerene derivatives had different polar groups on the side chain also had different wettability with ZnO,which also formed different surface topography on the surface of ZnO.For example,the fullerene derivatives C₆₀-4HTPB,C₆₀-PHFBS,C₆₀-2BEFPE,C₆₀-2TEBPE and C₆₀-2EHTPB with good wettability with ZnO can form uniform films on the surface of ZnO.While the fullerene derivatives C₆₀-2DPE,C₆₀-4TPB,C₆₀-PEHBS and C₆₀-2HMTPB with poor wettability with ZnO form pleated films on the surface of ZnO.The UPS measurement supported that different fullerene derivatives had differene effect on the enhancement of ZnO energy level.The best improvement is the triblock fullerene derivative C_60-2EHTPB,and the HOMO and LUMO energy levels of ZnO modified by C₆₀-2EHTPB can be increased from-7.88eV and-4.58eV to-6.79eV and-3.77eV,respectively,which is consistent with good wettability between C₆₀-2EHTPB and ZnO layer.（3）The self-organizing behavior of the amphiphilic fullerene derivative on the surface of ZnO was investigated by introducing toluene solvent treatment,and the behavior can be confirmed by X-ray diffraction（XRD）and surface contact angle test.With the treatment of toluene solvent,more hydrophilic blocks of the amphiphilic fullerene derivative will spontaneously align toward the ZnO end,while more hydrophobic blocks（fullerenes block）will face away from ZnO.The self-organizing behavior of amphiphilic fullerene derivatives could lead the carbon-rich block of fullerene to arrange in the opposite direction of ZnO surface,which also cuuse the obvious increasion of carbpn element of ZnO/fullerene derivatives sample measured by X-ray photoelectron spectroscopy（XPS）.（4）The amphiphilic fullerene derivative were also applied as cathode interface modification material in polymer solar cells（PSCs）based on the active layer of PTB7-Th:PC₇₁BM system,and different processes（solvent induction and non-solvent induction）were also introduced during the preparation of PSCs devices.It was found that the introduction of functional fullerene derivatives can effectively improve the interface compatibility between ZnO and the organic active layer,promote the transmission of electrons at the interface,and ultimately improve the photoelectric conversion efficiency（PCE）of the PSCs device.By comparing different processes,it was found that toluene solvent treatment had an opposite effect on the diblock fullerene derivative when applied as cathode interface materials in PSCs.While the solvent treatment also had obvious effect in enhancing the PCE of PSCs when introducing triblock fullerene derivatives as cathode interface materials.