CH₃NH₃PbI₃ Flexible Composite Films And Their Photodetectors

Organometallic halide CH₃NH₃PbI₃ is an ideal material for preparing photovoltaic devices such as solar cells,but its poor flexibility has always been an important reason limiting its development and application.With the rise of"wearable"concept,flexible photovoltaic devices are getting more and more attention.How to obtain flexible CH₃NH₃PbI₃ thin film materials is the basic problem to be solved in the application of flexible photovoltaic devices.Based on the properties of the existing materials,the organic-inorganic hybrid metal halide CH₃NH₃PbI₃ film is changed from"hard"to"soft"through the combination of organic metal halide and flexible substrate.it is hoped that the flexibility and mechanical properties of CH₃NH₃PbI₃ composite film material can be improved on the premise of considering the photoelectric properties.Firstly,perovskite-natural latex?CH₃NH₃PbI₃/NR?flexible composite films were prepared on natural latex elastic substrates by one-step spin coating method.The composition,structure and morphology of the composite films were characterized by UV-Vis diffuse reflectance spectroscopy,XRD and SEM.CH₃NH₃PbI₃ forms radially distributed fibrous crystals on the latex surface.The interdigital photodetector based on CH₃NH₃PbI₃/NR composite film has good photoelectric response characteristics,the light current intensity reaches microampere level,and the response is sensitive and stable.The effects of spin-coating preparation conditions and stress conditions on the photoelectric properties of composite films were studied.The results show that the best concentration of precursor solution is 2 M and the best spin coating rate is 2000 r/min.Under stress stretching,the deformation of the latex substrate causes the fibrous crystals of CH₃NH₃PbI₃ to break under stress,resulting in the degradation of the photoelectric properties of the composite film.However,the pre-stretching film forming method can not only effectively avoid the breakage of crystal fibers,but also improve the photoelectric response performance of the composite film,because the pre-stretching increases the degree of dense stacking of crystals in the film.Then,the film-forming properties of vapor-deposited CH₃NH₃PbI₃ crystals on different substrates were compared and studied.CH₃NH₃PbI₃ can crystallize and form films on BOPP,paper and nitrile rubber substrates by evaporation,and can withstand many friction bending tests without falling off easily.However,due to the weak adhesion of iodomethylamine to the latex,the film cannot be formed on the natural latex substrate,and only a yellow lead iodide film can be obtained.Vacuum evaporation method shows that there are higher requirements on the properties of substrate materials.Secondly,perovskite-cellulose paper?CH₃NH₃PbI₃/CP?composite films were prepared on cellulose paper by Shuang Yuan co-vacuum evaporation method and brush coating method,and single photodetector and array photodetector were prepared using the composite films.The composition,structure and morphology of the composite film were characterized by UV-Vis diffuse reflectance spectroscopy,XRD and SEM.The CH₃NH₃PbI₃ thin film material prepared by the co-vacuum evaporation method has good crystallinity,smooth surface,large coverage area,small crystal grains and uniform density.Flexible photodetectors have high sensitivity and fast light response,and show different photocurrent responses under different bending radii and bending angles.After 500bending cycles,the device can maintain over 75%of the initial photocurrent and has good stability against bending deformation.The 6×6 perovskite CH₃NH₃PbI₃ detector array prepared based on traditional origami technology shows that the photoelectric device has relatively good light acquisition capability through simple repeated stretching and folding,which provides basic research for three-dimensional image sensing.