Study On Preparation And Properties Of Wearable Perovskite Photodetectors Based On Flexible Substrates

In the information age,it is very important to detect the information from the complex environment.As the device for detecting optical signal,photodetector has important application value in military and civilian fields.The commercial photodetectors based on Si,Ge and Ⅲ-Ⅴ compound semiconductors have been developed maturely.Perovskite,as a new type of semiconductor,is expected to become a functional material of a new generation of photodetectors.Among them,organic-inorganic hybrid perovskite has many advantages,such as direct band gap,long carrier diffusion length and high absorption coefficient,so it can be used to prepare high performance photodetectors.With the development of the technology and the times,more and more devices are developing towards portable and wearable direction.The devices based on flexible substrates have been got more attention.Compared with other flexible substrates,there are many pores in the inner structure of cloth and paper,which is conducive to the filling of perovskite crystals.Based on the cloth and paper substrate,the low cost and wearable photodetectors are prepared by using hybrid perovskite MAPbBr₃.The specific work and achievements are as follows:1.The wearable photodetector based on polyester-cotton substrate is prepared.The precursor solution is drop-coated on the substrate and crystallized at 90℃.It is proved by a series of characterization that high quality perovskite crystals are obtained and the crystals are filled between the gaps of the fabric structure.By using the method of drop-coating,the high performance photodetector is obtained by selecting the appropriate number of drops.The responsivity of the device to ultraviolet light with a wavelength of 365 nm reaches 82 m A/W at a bias of 1 V,and the response time is only 32 ms.The device can also work without any bias,showing a high on/off ratio of 5×10³ and shows very good repeatability.The photocurrent is only reduced by 5.6%under ten minutes of continuous illumination,and the performance can be restored within 10 s after the light stops.Under different bending states,the photocurrent of the device will change accordingly,but it still maintains the same order of magnitude as the initial performance.The photodetector is directly prepared on the clothes and the result shows that the device can work normally in the wearing state.Because perovskite crystals are easy to decompose when meeting water and oxygen in the air,the protective layer is covered on the photodetector,which helps the device remain at the initial performance after at least 60 days.2.The highly deformable photodetector based on the paper substrate is prepared.By using filter paper as the substrate,the precursor solution is dropped on the filter paper and crystallized.The crystals are filled in the pores of the paper and distributes evenly.By adjusting the concentration and drop-coating times,the high performance photodetector is prepared.The maximum responsivity is more than 1 A/W,the on/off ratio is 10⁴,and the response time is about 30 ms.The device still has good performance under bending states,even if the current will decrease at the beginning of bending.The result after attaching to the finger joint proves that the device can work normally in wearing state.In addition,due to the characteristics of paper,the device is characterized and measured after twisting,crumbling and folding.The results show that the crystals are still firmly filled in the pores,and the performance of photodetector remains at about 50%of the initial value.In conclusion,two kinds of wearable and flexible photodetectors are prepared by using hybrid perovskite material MAPbBr₃.The devices have the advantages of low cost,environmental friendly and simple preparation,which promote the exploration of practical application of perovskite photodetectors.