Study Of Organic Photocoupler Based On The Photovoltaic Characteristics Of P3HT: PCBM

Organic electronics and optoelectronics have attracted a great deal of attentions because of their light weight, low cost, and potential applications for large area devices. In recent years many types of organic electronic and optoelectronic devices are commercially available, meanwhile the organic electronics and devices have become quite active. Organic photovoltaic devices become the focus of research because of the hoping to solve the energy crisis. Photocoupler is a new type device developed the 70's, applying in Electrical insulation, Level Translators and Switch circuit, but the high-cost silicon materials limited the inorganic photovoltaic devices widely used. With the development of organic semiconductor, Organic Light-emitting Diode and Organic Photovoltaic Device make great progress. So it is possible to fabricate an organic photocoupler. Compared with the inorganic photovoltaic devices the organic photovoltaic devices have many advantages, such as Simple Preparation, Low-cost and Flexible. In this situation, more and more study groups engage in the study of organic photocoupler.In this thesis, we aimed at the study of organic photocoupler based on P3HT:PCBM, and carried in three aspects mainly:Firstly, we have studied the energy conversion caused by the difference of input light wavelengths. The input light wavelengths we chose were 470nm, 520nm, 568nm and 624nm because of the absorption spectrum of P3HT:PCBM. The energy conversion efficiency of four devices were 2.37%, 1.7%, 0.7% and 0.26% when the input light wavelengths were 470nm, 520nm, 568nm and 624nm respectively. Meanwhile, the open circuit voltages of devices were 0.52V, 0.5V, 0.3 and 0.28V. Through our study, we found that the device based on P3HT:PCBM had high energy utilization ratio with short wavelength input light.Secondly, we have fabricated an organic photocoupler with organic light-emitting diodes as input unit and photodiode based on P3HT:PCBM as output unit. The relationship between the current transfer ratio (CTR) and output current with input light wavelengths was studied. The CTR of photocoupler we measured were 1.2%, 0.4%, 0.3% and 0.1% with the emission wavelengths of OLEDs were 470nm, 520nm, 568nm and 624nm respectively. Through our experiments, we got the conclusion that the short wavelength input light generates photocurrent and CTR efficiently.Thirdly, we have studied the influence of PEDOT:PSS buffer layer on the performance of organic photocoupler based on P3HT:PCBM. Through our experiments we have found that the output current is linearly increasing with the input current, the max output current and CTR of the device with PEDOT:PSS buffer layer are 2 times and 7 times than that of the device without buffer layer respectively, showing that the existence of buffer layer enhance the output photocurrent efficiently. Moreover, the existence of PEDOT:PSS eliminate the time delay of device.