Research Of High Efficiency Ternary Organic Solar Cells Based On PTB7:PC₇₁BM System

The organic solar cells（OSC）have the advantages of wide material sources,simple manufacturing process,low cost and so on,which has always been concerned.As an effective way to improve the performance of organic solar cells,ternary doping has attracted more and more research teams to conduct in-depth research in this filed.In this paper,based on the classical poly（{4,8-bis[（2-ethylhexyl）oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[（2-ethylhexyl）carbonyl]thieno[3,4-b]thiophenediyl}）（PTB7）:[6,6]-phenyl C₇₁-butyric acid methyl ester(PC₇₁BM)system active layer system,a-6T with properties of high carrier mobility,low cost and IEICO-4F with property of the near-infrared absorption are used as the third material respectively to prepare high-performance ternary organic solar cells and analyze the internal mechanism of performance improvement in detail.Firstly,the effect of high carrier mobility small moleculea-6T on the performance of PTB7:PC₇₁BM OSC was investigated.When the doping ratio ofa-6T is 1.0 wt%,2.0wt%,3.0 wt%,the device performance is improved.Especially when the doping ratio is2.0 wt%,the fabricated ternary organic solar cell has the best performance,the power conversion efficiency（PCE）is up to 8.09%which is 22.2%improvement compared with binary device with the PCE of 6.62%.It can be seen from the analysis that the main reasons for the performance improvement of the device are as follows:（1）the absorption spectrum ofa-6T makes up for the weak absorption of PC₇₁BM in short band to some extent,and the F（?）rster energy transfer betweena-6T and PTB7 enhances the ability of capturing photons;（2）a-6T incorporation can also modulate the morphology of the active layer and regulate the degree of phase separation between the donor and the acceptor;（3）the incorporation ofa-6T greatly improves the electron and hole carrier mobility of the device,which is helpful to the charge transport and collection.Secondly,the effect of infrared absorption material IEICO-4F on the performance of PTB7:PC₇₁BM OSC was investigated.When the doping ratio ofa-6T is 1.0 wt%,2.0wt%,3.0 wt%,the device performance is improved.Especially when the doping ratio is2.0 wt%,the fabricated ternary organic solar cell has the best performance,the power conversion efficiency（PCE）is up to 7.96%which is 19.3%improvement compared with binary device with the PCE of 6.67%.It can be seen from the analysis that the main reasons for the performance improvement of the device are as follows:（1）the infrared absorption characteristic of IEICO-4F broadens the optical absorption range of the device from 380nm-850nm to 380nm-1000nm;（2）IEICO-4F,PTB7 and PC₇₁BM form an appropriate energy level gradient arrangement,which can introduce charge transfer mechanism in device making the charge more easily transmitted and collected;（3）the introduction of IEICO-4F can effectively improve the morphology of the active layer and the phase separation between the donor and acceptor,and reduce the probability of exciton recombinationIn summary,this paper provides the reference of material selection and theoretical guidance for the preparation of high-performance ternary organic solar cells,which has certain reference significance for the commercial production of organic solar energy...