| Compared with traditional inorganic photodetectors,organic photodetectors have the advantages of wide selection of materials,easy control of structure and function,wide detection spectrum,simple preparation process,etc.,so they have gradually become a hot research direction of photodetectors.However,the functional materials of the organic photodetector,especially the organic functional layer,are easily corroded by water vapor and oxygen in the environment,which makes the performance of the device degrade quickly in the ordinary atmospheric environment.Therefore,in order to extend the life of the organic photodetector,it is necessary to add the packaging protection layer to isolate water and oxygen in the environment.At present,there are two main packaging schemes for organic photodetectors,one is glass cover packaging,and the other is thin film encapsulation.This article mainly focuses on thin film encapsulation technology to carry out related research work.The main research contents of this paper are as follows:First,an organic photodetector based on the bulk heterojunction structure was prepared,and the main photoelectric properties of the device before encapsulation were analyzed and tested,and the photocurrent attenuation of the unpackaged device was investigated with time.The test results show that the lifetime of the device（the device lifetime is defined as the time required for the photocurrent to decay to half of the initial value）is less than one week when the detector is unpackaged in the presence of ordinary atmospheric conditions.In order to effectively extend the life of the fabricated device,this article first adopts a single-layer thin film packaging scheme.Inorganic aluminum oxide film is selected as the film material,and the protective effect of aluminum oxide film prepared by two processes,electron beam and atomic layer deposition（ALD）is emphasized.The test results show that the water vapor transmission rate（WVTR）of the alumina film prepared by the two processes can reach 10-2-10-3g/m2/day and 10-3-10-4g/m2/day;respectively and the life of the organic photodetector is extended to more than 140 and 200 hours after being protected by the two kinds of aluminum oxide films.In order to further enhance the protective effect of the encapsulation layer,this paper adds an organic film on the aluminum oxide film prepared by the ALD process to form an inorganic/organic laminated protective structure.Firstly,we compared the optical transmittance,surface roughness and water vapor transmittance of two common organic encapsulation protection materials—Parylele-C（monochloro-substituted polyparaxylene）and PDMS（polydimethylsiloxane）.Although the water vapor transmission rate of PDMS is slightly higher than that of Parylele-C on the surface of the structure,it has better overall performance（higher optical transmittance and lower surface roughness）,so PDMS is selected in this article.Multi-layer thin film were prepared with different cycles of laminated structure（1cycle=alumina/PDMS,2cycle=alumina/PDMS/alumina/PDMS...）,and their water vapor transmission rates were tested.The results show that the water vapor transmission rates of the laminated structure of 1 cycle and 2 cycle are 4.7×10-5g/m2/day and 6.8×10-6g/m2/day,respectively.However,as the number of cycles further increases,the reduction in water vapor transmission rate is not significant(3.1×10-6g/m2/day at 5cycles),but the stress increases a lot,causing the device encapsulation layer to easily crack.Therefore,in this paper,a 2 cycle laminated structure is finally used to encapsulate and protect the prepared detector.The test results show that the life of the device after protection exceeds 600 hours（20°C,50%relative humidity）. |
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