Ammonia Sensitivity Of Perylene Diimide Organic Heterojunction Sensor

Ammonia（NH₃）is not only an important industrial material,but also an important raw material for agricultural production.It has important economic status,and is harmful to human body.In the fields of chemical refining,environmental protection,mining and metallurgy,ammonia detection is required.At the same time,ammonia is also a respiratory marker of human chronic kidney disease,and the realization of portable detection is of great significance for Industrial production and disease prevention.In this paper,combining the filling effect of accumulation effect on the trap state,the mutual excitation of carriers on both sides of the heterojunction,and the large change of channel resistance in the continuous layer,and combines the characteristics of perylene diimide derivative film,which is extremely thin,large specific variation area and sensitive to ammonia gas,to prepare an ammonia sensor with high sensitivity,fast response,and high repeatability.Firstly,the gas sensitivity of single layer perylene diimide derivative BFPDI to ammonia was studied.BFPDI was synthesized by introducing 2,3,4,5,6-pentafluoraniline into the amide position of perylene diimide.The properties of BFPDI were characterized and its energy level was determined by electrochemical method.Based on this,the BFPDI film ammonia sensor was fabricated.The gas sensitive parameters such as response recovery time,sensitivity,repeatability and stability were tested.The process of free radicals generated by the interaction between single layer BFPDI film and ammonia gas and the change of film resistance were discussed and analyzed.Secondly,the heterojunction structure was introduced to improve the reaction rate of perylene diimide to ammonia.The BFPDI/TFPDI organic homojunction device was prepared by introducing 2,3,5,6-tetrafluoro-4（-trifluoromethyl）aniline into the amide position of perylene diimide.The material characteristics of TFPDI were characterized.From the perspective of energy level difference,combined with the change of carrier distribution on both sides of the heterojunction interface,the reason for the improvement of ammonia reaction speed by heterojunction structure was explained.Lastly,the application of P-type/N-type organic heterojunctions with stronger accumulation effect in ammonia sensing is studied.A heterojunction model with bilateral carrier accumulation effect was constructed,and the interface energy level difference was combined with organic-organic interface energy level alignment theory（OOI-ELA）and experimental results to verify that the interface potential barrier was conducive to the formation of heterojunction accumulation.On this basis,the device was fabricated by pentacene and BFPDI.After testing,it was found that compared with the single-layer BFPDI ammonia sensor,The gas-sensitive characteristics of the device such as response recovery time and sensitivity are improved.Through the film morphology and accumulation effect model,the mechanism of the heterojunction device effectively improving the reaction speed and sensitivity is analyzed.