Preliminary Investigation Of Physical Mechanism In Ternary Heterojunction Solar Cells Based On Novel Optoelectronic Materials

The main problems limiting the development of organic solar cells are low efficiency and poor stability.The low efficiency of organic solar cells is mainly due to the low utilization rate of sunlight.In order to overcome the low utilization rate of solar spectrum of organic solar cells and enhance the ability to capture photons,new photoelectric materials PM7 and Y6 are used as the materials of organic solar cells with heterojunction,IT-4F with complementary absorption spectra and matching energy level structure is selected as the third component of the device,and the ability of photon capture and transmission is improved through ternary heterojunction strategy.At the same time,the optical physics,exciton disintegration,conductance and carrier mobility of the device are studied,and the mechanism of the device is further studied.Another major problem is stability.This paper tested and studied the stability of devices.The main work is summarized as follows:(1)By changing the ratio of acceptor,the thickness of active layer and the annealing condition,the optimal preparation conditions of the device were obtained,and the efficiency of the device could reach 14.59%.The additive can significantly change the morphology and structure of the active layer.Using additive CN,the efficiency of the device can reach 15.23%,It is proved that the internal structure of organic film is more reasonable.(2)By controlling the proportion of the third component IT-4F,the ternary heterojunction organic solar cell based on PM7:Y6:IT-4F was prepared,and the highest efficiency of the device reached 16.60%.The photophysical properties of the active layer,namely absorption spectrum and EQE,were analyzed.The results show that the proper IT-4F is helpful to improve the utilization of sunlight in the device,and promote the conversion of excitons into charge which is collected by the electrodes at both ends.Excited state carrier exciton generation and dissociation shows that the rate of exciton generation and dissociation probability of ternary heterojunction device is high.IT-4F can reduce the recombination of charge,so IT can get larger Jsc and Voc.The analysis of AC impedance spectrum shows that the capacitive reactance of ternary heterojunction device is mainly generated by the capacitance at the interface,and the increase of composite resistance is helpful to restrain the exciton recombination.The measurement and analysis of charge mobility indicate when PM7:Y6:IT-4F is 1:1.2:0.10,the disintegration of the device is the maximum,and the ratio of electron mobility-e to hole mobility-h is close to 1,which is in the most balanced state.The study on the morphology of the active layer shows that the film has low roughness and smooth surface,and the materials are fully integrated with each other.(3)Explore the stability of the device.The stability of the bulk heterojunction device and the ternary heterojunction device in the glove box and outdoor non-light conditions was tested.It is found that the device in the glove box is more stable than the device outside,and the ternary heterojunction device is more stable than the bulk heterojunction device.It shows that IT-4F can improve the efficiency and stability of the device.The hydrophobic angles of the ternary organic solar cells based on PM7:Y6:IT-4F are all greater than 90°,indicating that the devices have strong hydrophobicity.Under AM1.5G light conditions,the performance of the device in the glove box decays for the first 50 h,then the device gradually stabilizes after 50 h,the 60% that decays to the initial efficiency of 16.6% stabilizes at 10%.This article has a total of 26 figures,11 tables and 110 references.