Preparation And Characterization Of Bulk-Heterojunction Ternary Organic Solar Cells

Looking back at the three industrial revolutions that humans have carried out,every industrial revolution is inextricably linked to the use of energy.From the fossil fuel of internal combustion engines to the full utilization of electrical energy,to the development of atomic energy,all are accompanied by advances in energy use.However,with the rapid development of human society,people's material living standards have been greatly improved.Meanwhile human demand for traditional energy sources is increasing.The excessive exploitation and use of limited traditional fossil fuel energy by humans has directly led to a severe energy situation and a deteriorating ecological environment.Organic solar cells are an inexpensive renewable energy source,which has attracted wide attention from researchers because of its advantages of easy preparation,light weight,flexibility and abundant raw materials.Ternary organic solar cell is used to increase the energy conversion efficiency of a polymer photovoltaic device by introducing a third component?donor or acceptor?into the host host system to broaden the absorption spectrum of the functional layer.Recently,ternary organic solar cells have developed into a research hotspot.In this paper,ternary polymer solar cells based on PTB7-Th:PC₇₁BM:IT-M system,PTB7-Th:PC₇₁BM:PBDB-T system and PBDB-T:ITIC:ICBA system were studied.In the second chapter,the performance of the photovoltaic device of the PTB7-Th:PC₇₁BM binary system was improved by introducing the medium band gap non-fullerene material IT-M in the PTB7-Th:PC₇₁BM system.When the introduction quality of IT-M is 15wt%,the energy conversion efficiency?PCE?of organic photovoltaic devices is as high as 9.87%,which is16%higher than that of binary organic photovoltaic devices.The main mechanism for improving the PCE of organic photovoltaic devices can be attributed to the enhancement of the spectrum absorption intendensity of the active layer by introducing IT-M into the PTB7-Th:PC₇₁BM system.The energy level cascade between the materials increases the channels of the electron transport in the active layer and improves the contact area between the active layer and the interface layer.In the third chapter,we demonstrate that efficient ternary OSCs can be obtained by combining the polymer donor PBDB-T with the ideal complementary absorption coverage with the PTB7-Th:PC₇₁BM system.When the ternary OSCs based on PTB7-Th:PBDB-T:PC₇₁BM were optimized,it was found that the optimal PCE of ternary OSCs reached 9.45%when the optimal weight ratio of PBDB-T in the donor was 15wt%.J_SC was 17.67 mA/cm²,V_OC was0.808 V,and FF was 66.18%.Our results show that the extended absorption spectrum of the three components promotes the generation of excitons and helps to improve device performance.There is a non-radiative FRET pathway from PBDB-T to PTB7-Th.Because of the energy level cascade between the ternary components,there are three ways of charge transport in the ternary OSCs,while only one exists in the binary system.This energy and charge transfer mechanism plays an important role in improving the energy conversion,charge dissociation and collection efficiency of the device,thereby reducing the probability of charge recombination.Our results also provide guidance for selecting a third component having an energy level similar to the host material to obtain efficient ternary PSCs.In the fourth chapter,we prepared efficient ternary OSCs based on PBDB-T,ITIC,and ICBA.As the third component of the ternary,ICBA can affect the intermolecular?-?interaction of ITIC and the morphology of mixed active layers due to its inherent amorphous nature.Effective photogenerated exciton generation and dissociation,balanced charge mobility and optimized film morphology explain this high photovoltaic performance of the three components.In the end,we obtained 10.23%of PCE by additionally introducing 10wt%ICBA to the ternary system.