Research Of Ternary Organic Solar Cells Based On Soluble Small Molecule Donors

As one of the most promising green energy supply methods,organic solar cells?OSC?are characterized by light weight,flexibility,large area and environmental protection,and have been widely concerned in recent years.Among them,the ternary organic solar cell can broaden the spectral absorption,increase the carrier mobility and improve the device morphology,so it is a simple and effective strategy for improving the performance of the traditional binary organic solar cell.In this paper,soluble small molecular materials are combined with traditional binary organic solar cells to fabricate high-efficiency ternary organic solar cells.The main work is as follows:1.For the first time,a new indole imidazole derivative?PyPI?was incorporated into the classical binary PTB7-Th:PC₇₁BM system to construct a highly efficient ternary organic solar cell.The ternary OSC based on PTB7-Th:PyPI:PC₇₁BM exhibited a high power conversion efficiency?PCE?of 10.36%,with the short-circuit current(J_SC)and fill factor?FF?were improved to 19.26 mAcm^-2 and 67.90%,respectively.Compared with the binary device,the performance was improved by 15.88%.At the same time,the ternary OSC showed better heat and light stability.Under continuous 60?C annealing for3 h,in atmosphere,the device efficiency still remains at 94.13%more than the pristine state,while the control device PCE remains at 52.47%.Constant illumination under Air Mass?AM?1.5G irradiation(100 mWcm^-2)in atmosphere,the PCE of OSC remains at72.50%.Through a series of tests and analysis,it was found that PyPI can form effective?-?stacking in films,while the stacking of small molecule PyPI can promote charge transfer and inhibit fullerene aggregation,which is the main reason for the improvement of performance and stability.2.A soluble organic small molecule DFNPy with fused ring structure was proposed.The ternary OSC based on PTB7-Th:DFNPy:PC₇₁BM was designed and prepared,which PCE was 10.59%with an enhanced J_SC of 19.72 mAcm^-2 and FF of 68.15%.DFNPy shows complementary absorption spectra in the 350–450 nm shortwave band,which has seldom been reported in the field of ternary OSCs.In addition,bulky benzene ring structures can form?-?stacks to promote charge transfer.The addition of DFNPy can improve the phase separation and crystallinity of the membrane,optimize the morphology of the membrane,promote charge generation and reduce charge recombination,thereby increasing the mobility and ultimately improving the performance of the traditional binary system.In this paper,soluble small molecules which are easy to form?-?stacks are introduced into the traditional binary system,and a highly efficient ternary organic solar cell is realized.The influence of?-?stacking effect on three components is systematically analyzed,and is a new solution for improving the performance of organic solar cells.