Research On The Effect Of Spin In Bulk Heterojunction And Thermal Delayed Fluorescence Devices On Photoelectric And Thermoelectric Properites

The use of bulk heterojunction and the appearance of thermal delayed fluorescent material are effective to improve the efficiency of the organic thermoelectric and lightemitting devices,respectively.The two kinds of devices' internal carrier charge-spin coupling mechanism and mutual transformation between spin are also more unique and rich.But the research on how to improve the performance of devices by spin is still imperfect.Bulk heterojunction thermoelectric devices and thermal delayed fluorescence devices were used as research objects by regulating the external magnetic field and the thickness of the ferromagnetic materials,exploring the change of thermoelectric,absorbing,lighting,magnetic field effect and ferromagnetic resonance.Furtherly,experimental results combined with theory model analyzed how the spin and spin interaction affect the internal charge movement and external performance.It provides a new idea for further improving the efficiency of the thermoelectric and light-emitting devices.The main contents of the paper are as follows:Firstly,the spin test platform was established to test spin interactions in organic conjugated semiconductors,which are used in organic thermoelectric devices and thermal delayed fluorescence devices to study how spin and spin interactions affect internal carrier motion.Secondly,the thin-film thermoelectric device with ITO/P3HT:PCBM/ITO structure was prepared,and the thermoelectric performance of the device was effectively improved by increasing the density of excited states.When external magnetic field is applied under high temperature,the Seebeck coefficient of the pure P3 HT devices increases with the increase of the magnetic field,and the magnetic field effect also increases with the increase of temperature.For P3HT:PCBM devices,the Seebeck coefficient decreases with the increase of the magnetic field,but the magnetic field effect increases with the increase of temperature.Based on the exciton-charge theoretical model and the polaron pair theoretical model,the internal principles of change and the role of spin in the change are analyzed,which provide new ideas for improving the performance of thermoelectric devices.Thirdly,4CzTPN-Ph taken as the research object,a Ni/4CzTPN-Ph based luminescent device was prepared,and the influence of temperature and Ni thickness on the photoluminescence magnetic field effect and electronic paramagnetic resonance signal was systematically studied.Studies have found that the application of a ferromagnetic layer can increase the half-width of the photoluminescence magnetic field effect,and with the increase of the Ni thickness,the effect gradually becomes obvious.As the thickness of Ni increases,the light-induced EPR signal also decreases.When Ni is thickened to 15 nm,both the EPR signal and the photoluminescence magnetic field effect are unobservable.On this basis,Ni was introduced into the organic light-emitting diode device with 4CzTPN-Ph as the light-emitting layer,and the efficiency and luminance of the device were characterized,and the influence of the ferromagnetic/organic interface on the performance of the device was preliminarily studied.It provides an effective means for using ferromagnetic materials to achieve spin injection to improve device performance.