Synthesis Of Porous Aromatic Frameworks And Their Applications For Perovskite Solar Cells

As concerned with environmental degeneration and traditional energy consumption,people are focused on novel renewable energy sources.Among various applications of renewable energy sources,solar cells have attracted much attention because of inexhaustible energy source free from restriction of region.Perovskite solar cells?PSCs?have bloomed as one of the most promising photovoltaic devices within a few years.As a key part of PSC,hole-transport material?HTM?commonly is Spiro-OMeTAD for forward PSCs and PEDOT:PSS for inverted PSCs.However,these HTMs are expensive,lack of stability,and corrosive to substrates,which limit the life time of PSCs and their commercialization.Porous aromatic frameworks?PAFs?,with excellent properties of porosity,large specific surface area,and high chemical,thermal,and mechanical stabilities,have been proven to have superiorities in terms of gas storage and separation,heterogeneous catalysis,electricity,and sensors.Herein,we introduce PAFs as HTMs into PSCs with low-cost,high stability and simple production process,which efficiently solve the difficulties of cost and energy consume as well as poor stability during the course of industrialization.Firstly,PAF-87 containing triphenylamine with hole-transport property is synthesized through the simple Scholl Reaction followed by a series of characterization.PAF-87 shows high specific surface area and outstanding chemical stability.When it is used as HTM in forward PSC,the power conversion efficiency remains to be improved due to the insoluble nature of PAF-87,which resulting in a poor film forming property.Secondly,in order to overcome the insolubility of PAFs and improve the film forming property,three PAFs?PAF-88,PAF-89 and PAF-90?are in situ synthesized on ITO glass through electropolymerization.A series of characterization display that PAF films synthesized through electropolymerization possess smooth and dense surfaces,for instance the roughness of PAF-88 surface is only 5.26 nm.The three PAFs own appropriate work founction to match the valence band of CH₃NH₃PbI_xCl_3-x as well as high LUMO levels to block the electrons.The PAF-89holds the highest hole mobility of 9.73×10^-8 cm² V^-1 s^-1.The three PAFs are deposited on PEDOT:PSS to form composite HTMs applying in inverted PSCs,the PAF-90 performs the best power conversion efficiency of 7.13%that is close to the PEDOT:PSS-based PSC?7.39%?.Meanwhile,the stability is improved significantly.After storing at room temperature in the air without encapsulation for 48 h,the PSC based on composite HTM can retain 60%of the initial photovoltaic performance,whereas the PEDOT:PSS-based PSC decrease to 27%in the same condition.Thirdly,for the sake of improving the hole mobility of PAF materials,PAF-86and PAF-91 are designed and synthesized through electropolymerization method.The property and structural characterization of the two PAFs reveal that they both have smooth and dense surface with excellent chemical and thermal stability.Moreover,the two PAFs both own the ability of hole extractin and electron blocking towards CH₃NH₃PbI_xCl_3-x.Furthermore,the PAF-86 holds a high hole mobility of10^-5 cm² V^-1 S^-1.A high power conversion efficiency of 10%is obtained when PAF-86 is used as HTM in inverted PSC for the first time.The stability test shows that PSC based on PAF-86 can maintain 80%of its performance after storing for 500h without encapsulation in the air,whereas the PEDOT:PSS-based PSC significantly decreased to 4%under the same conditions.This work broadens the application areas for PAFs and exploits a simple process to synthesize HTMs with high efficeiency and superior stability as well,which promotes the progress of PSCs for civil and commercial applications.In addition,this work will also be favorable to the fields of catalysis,fuel cells,hydrogen generation,and organic matter decomposition and so on.