A Research Of High-Efficiency Ternary Organic Solar Cells Based On Luminescent Dyes

Organic solar cells?OSCs?are envisioned to be developed into the next generation photovoltaic technology owing to their low cost,flexibility,light weight and easy fabrication by solution processing and/or roll-to-roll manufacturing.Insufficient spectral absorption,unbalanced carrier mobility,and recombination loss are the main reasons that limit the device efficiency further improvement.In this paper,the ternary strategy was adopted in order to solve these problems.The fluorescent dyes C545T and Coumarin7?C7?were first doped into the PTB7-Th:PC₇₁BM and PTB7:PC₇₁BM host systems as the third component and eventually resulted in a significant increase in device performance.This paper mainly elaborates on the following aspects:1.For the first time,C545T was doped into the PTB7-Th:PC₇₁BM host system to fabricate ternary OSCs.The energy level,absorption spectrum and surface energy test show that C545T meets the basic conditions as the third component.The ternary device PTB7-Th:C545T:PC₇₁BM finally achieved the highest efficiency of 10.69%,and efficiency increase exceeds 20%compared to the host system.By characterizing the spectral characteristics,film morphology,and electrical properties of the devices,we have found that C545T can not only optimize the exciton transport path by transferring energy to polymer donor,but also modulate the severe vertical distribution through the?-?stacking with the PC₇₁BM so as to effectively improve the phase-separation domain size,exciton diffusion domain width,and charge transport domain length.Therefore,the spectral absorption,exciton dissociation efficiency,charge mobility,and recombination loss of the device are significantly improved at the same time and eventually promote the improvement of the device efficiency.2.Based on the vertical modulation mechanism of C545T,in order to investigate whether the luminescent dyes can generate other interactions with the host system that are conducive to the device performance,we also doped C7 as the third component into the PTB7-Th:PC₇₁BM to fabricate ternary OSCs,and finally achieved the champion device efficiency of 12.45%,which was more than 30%higher than that of the host system.This is due to the fact that the intermolecular hydrogen bonding can be formed between C7 and PC₇₁BM,which not only greatly enhances the electron-drawing ability of PC71BM,but also optimizes the nanofiber morphology of bulk heterojunction and phase separation domain size.Therefore,the spectral absorption,charge mobility and single-double molecule recombination are simultaneously improved and eventually promote the enhancement of device efficiency.3.In order to ascertain whether C545T and C7 will play a similar role in other host systems,we also doped them into the PTB7:PC₇₁BM host system to fabricate ternary OSCs.The test results show that the main regulation mechanisms of C545T and C7 in the two main systems are the same,and the ternary devices PTB7:C545T:PC₇₁BM and PTB7:C7:PC₇₁BM finally achieved device efficiency of 9.42%and 10.28%,respectively.In this paper,the traditional organic light-emitting materials are successfully applied in the field of organic photovoltaic cells for the first time,and it is proved that the luminescent dyes can also effectively improve the photoelectric performance of the devices through ternary OSCs strategy.Therefore,this paper broadens the choice of OSCs materials,and has certain reference significance for the synthesis of organic photovoltaic materials and the fabrication of ternary OSCs in the future.