Study On The Performance Of Organic Solar Cells Based On Double Cathode Interface Layer

With the continuous development of the world,energy consumption and environmental pollution are also increasing.The development of pollution-free,renewable new energy is in line with the needs of social and economic development in the new era.Therefore,many new renewable energy sources have been developed.Among them,solar energy derived from the fusion radiation inside the sun is considered to have a high social application status due to its advantages of wide distribution,huge storage capacity,can be used anywhere and no pollution to the environment.The development of solar cells has become a direct way to use solar energy.In recent years,due to its wide material sources,simple production process,light weight of the product,and can be processed into flexible battery through roll-to-roll production,organic solar cells have become a hot research topic.Even if its power conversion efficiency has exceeded 17%,organic solar cells are not suitable for large-scale commercial production yet.The interface optimization of organic solar cells is a feasible method to improve the energy conversion efficiency of organic solar cells.The interface modification layer can be prepared at the interface between the electrode and the photosensitive layer,its main function is to reduce interface defects,change the work function of the electrode to match the energy level of the photosensitive layer,and accelerate the transfer of charges,thereby improving the performance of the organic solar cell.This paper mainly focuses on the interface modification of the electron transport layer,the content is as follows:1.By using Sn O₂/Alq₃ as the dual cathode interface layer,we have prepared an organic solar cell with the structure of ITO/Sn O₂/Alq₃/P3HT:PC₆₁BM/Mo O₃/Ag,and compared with the device using Sn O₂single cathode interface layer,the energy conversion efficiency has increased from 3.09%to 4.08%.The insertion of the Alq₃layer improves the surface flatness and hydrophobicity of the Sn O₂film,and improves the interface contact and energy level matching with the photosensitive layer.The double-cathode interface improves the rectification characteristics of the device,reduces the leakage current and series resistance,improves the electron transport capacity,and inhibits the recombination of photo-generated carriers.The device has obtained higher J_sc and FF,which improves its efficiency.2.An inverted organic solar cell with a structure of ITO/Sn O₂/Ca F₂/PCDTBT:PC₇₁BM/Mo O₃/Ag was fabricated.The Sn O₂cathode interface layer is modified by evaporating a thin layer of calcium fluoride（Ca F₂）to improve the performance of organic solar cells and has achieved a PCE of 6.97%,which is about20%higher than the PCE of the comparative device without Ca F₂ modification.The increase in PCE of organic solar cells is due to the higher electron pumping capacity and conductivity of the Sn O₂/Ca F₂ double layer,which reduces the leakage current and equivalent series resistance of the device;Ca F₂ layer forms a dipole layer between the Sn O₂ layer and the photosensitive layer,which adjusts the work function and energy barrier at the interface,improves the efficiency of electron transport,and reduces the carrier recombination at the interface between the photoactive layer and the Sn O₂ layer.In addition,the Ca F₂ layer also improves the hydrophobicity of the surface of the Sn O₂layer,which helps to improve the compatibility between the Sn O₂layer and the photoactive layer.The results show that Ca F₂ modified Sn O₂cathode interface layer is an uncomplicated and valid measure to improve the property of the cells.