Effects Of Interfacial Modification Layers On The Performance Of Organic Photovoltaic Cells Based On C₆₀ Acceptor

With further development of industralization, the excessive use of coal, oil, natural gas and other non-renewable fossil fuels not only leads to increasing energy supply crisis, but also causes serious pollution and destruction to the environment. Therefore, as an ideal and clean energy source, solar photovoltaic cells have become the focus of attention in this area and made great progress. However, in order to make solar cells being applied in industry, its power conversion efficiency（PCE） and working life are desperate to be improved. In addition to the donor and acceptor materials, the interface modification has a direct effect on the performance of such cells. Hence, it is of great significance to develop cathode or anode interface modification with better properties, which is one of hot issues in the current research. In this thesis, we have studied the effect on the performance of cells when inserting different double cathode and anode modifications and based on CuPc/C₆₀ and SQ/C₆₀ planar heterojunction orgabic solar cells. The specific work is as follows:（1） We fabricated a reference cell with the structure of ITO /MoO₃ /SQ /C₆₀ /BCP /Al based on SQ/C₆₀ active layer. To study the problem of cathode interfacial modification, we designed three double cathode interfacial modifications including Bphen/BCP, TPBi/BCP and Alq₃/BCP and inserted them to the reference cell. The effects of changing the thicknesses of Bphen, TPBi and Alq₃ on the performance of the cells were under the condition of keeping the thickness of BCP. When the thickness of Alq₃ was 3 nm in Alq₃/BCP double modification, the short-circuit current density（Jsc） was 10.15 mA/cm2 and the corresponding PCE was 3.09 %, which were increased by 3.5 % and 9.6 % compared with those of the reference cell, respectively. Furthermore, we fabricated a reference cell with the structure of ITO /MoO₃ /CuPc /C₆₀ /BCP /Al based on CuPc/C₆₀ active layer. Three same double cathode interfacial modifications were also introduced into the reference cell. The Jsc was increased by 101 % to 8.98 mA/cm2 and the highest PCE was developed by 69 % to 1.83 % when the thickness of Alq₃ was 3 nm in Alq₃/BCP modification layer. Therefore, the Alq₃/BCP double modification layer with a thickness of 3 nm Alq₃ improved the performance of cells significantly. We prepared a single-carrier electron-only device with the structure of ITO /Al /Alq₃ /BCP /Al and tested the current-voltage curves. The results showed that adding the double cathode interfacial modification prompted the formation of ohmic contact on the interface between the modification layer and the cathode to enhance the electron extraction capacity. The improvement of the cell performance could also be attributed to restraining the quenching of the excitons at one side of the cathode with the addition of the double cathode interfacial modification.（2） We designed three double anode interfacial modifications including MoO₃/NPB, MoO₃/TcTa and MoO₃/Alq₃ on the basis of MoO₃ anode buffer layer and inserted them to the reference cell based on SQ/C₆₀ and CuPc/C₆₀ reference cells. The effects of changing the thicknesses of NPB, TcTa and Alq₃ on the performance of the cells were studied by keeping the thickness of MoO₃ unchanged. In SQ/C₆₀ cells, when the thickness of NPB was 3 nm, the open circuit voltage（Voc） was increased from 0.62 V to 0.66 V and the PCE reached 2.80 % which was lower than the PCE of the reference cell 2.82 %. In CuPc/C₆₀ cells, the Jsc 4.50 mA/cm2 which was higher than that of the reference cell slightly and the corresponding PCE was basically unchanged. The possible reasons included higher hole-transport barrier and lower light transmittance of the cells after the introduction of double anode interfacial modifications. Although the single MoO₃ layer was still a better anode interfacial modification material among double anode interfacial modification materials, more research needed to be carried out to obtain better anode interfacial modification materials.