Study On Red-sensitive Photodetectors Based On CuPc/C60 Heterojunction

Photodetector is the photoelectronic device,which converts light into electrical signal.Compared to inorganic photoelectric detector,the parameters of the Organic Photodetector?OPD?performance is improved,and the the advantages of OPD are light,flexible and compatible with large areas.Photoactive layer materials can also play an important role in regulating the color recognition.Those characters of OPD make them have incomparable advantages in the flexible components,wearable device and short distance optical fiber communication and other fields.In this paper,in order to study the OPD applied for optical communication of local-area network as optical receiver,red light has lower optical loss coefficient,red-sensitive photodetectors is key to organic optical communication of local-area network.We chose the traditional CuPc/C60 plane heterojunction structure.In order to get lowerdark current and increased responsivity,we did the specific work is as follows:?1?The glasses with ITO anode were used as the substrate,the Planar heterojunction CuPc/C60 was deposited by thermal evaporation technology.To balance the CuPc optical absorption and exciton transmission,the thickness of the CuPc was optimized.The thickness of C60 is 40 nm,when thickness of CuPc is 60 nm,the photocurrent is the largest.?2?Plane heterojunction CuPc/C60 is furtherly studied to reduce the dark current.In order to reduce the dark current,the influence of inserting Ir?ppz?₃ on device performance device is studied,the structure of ITO/CuPc?60nm?/C60?40nm?/Ir?ppz?₃?2nm?/Al was fabricated.Compared to the device without Ir?ppz?₃,dark current density reduced by 6% and the ratio of the photocurrent to the dark current increased by 10.7%.Nextly,we studied how the different thickness of Ir?ppz?₃ affect the performance of the device,the structure of ITO/CuPc?60nm?/C60?40nm?/Ir?ppz?₃?z?/Al was fabricated,z of these five components was 0,0.5,2.5,5,10 nm.With the increased thickness of Ir?ppz?₃,the dark current was lower.When the thickness of Ir?ppz?₃ was 0.5 nm,due to the buffer layer is too thin to effectively restrain dark current,when the thickness of Ir?ppz?₃ is 10 nm,photo-electrons is not sufficient to penetrate the buffer layer by tunneling effect.The study found that when the thickness of Ir?ppz?₃ was 5 nm,integrated performance of the OPD is optimal,the dark current density of the device is 0.09 mA/cm2.?3?Without buffer layer device structure: ITO/CuPc?60nm?/C60?40 nm?/Al was fabricated on flexible PET substrate.Pentacene were introduced to replace the same thickness of CuPc to take advantage of the double carrier transmission characteristics of CuPc,and a cascade-energy-level alignment OPD was studied by stacking three materials with appropriate HOMO and LUMO energy levels.Compared between the OPD with 6nm Pentacene and the one without Pentacene,the responsivity increased by 19.7%.We fabricated the OPD on the flexible PET substrate as same the structure as the one deposited on glass with 5nm Ir?ppz?₃,then inserting 5nm Pentacene in the C60 to form new heterojunction.Under 3V reverse bias,despite of slightly lower responsivity of the device,from 77 to 68 mA/W,but dark current density reduced significantly from 0.1mA/cm2 reduce to 0.04mA/cm2,and the ratio of the photocurrent to the dark current was also improved,and we did bend test and get good good performance.Those studies make full preparations for getting portable flexible image sensors.