Research On High Efficiency Ternary Organic Solar Cell Based On Fullerene Acceptor

Organic solar cells?Organic solar cells,OSCs?as one of the most promising renewable energy technologies have attracted widespread attention due to their low cost,light weight,and the ability to make flexible devices.However,due to some shortcomings of organic materials,such as the small absorption range and the inability to directly generate charge holes,the development of OSCs has been limited.In order to overcome these shortcomings,researchers have developed a series of methods.The ternary OSC is a method for improving device efficiency by adding a third material to a binary active layer.There are various aspects of the role played by ternary materials in OSCs,such as optimizing energy level matching,broadening the range of absorption spectrum of active layers,improving the morphology of thin films,and promoting carrier migration,etc.Generally,a ternary material will have multiple effects.In this paper,circular small molecules are added to the fullerene system PCBM and PC71BM as the third component,which effectively improves the efficiency of the device,and the specific role of small ring molecules in OSCs was discussed by means of calculation and experiments.The main contents of this article are as follows:?1?The concept of[9]CPP???C₆₀ supramolecular was introduced into the C₆₀ derivative PCBM fullerene OSCs.The small circular molecule[9]CPP and 7+Pyrene were added to PTB7-Th:PCBM as the third component materials,respectively,to construct the ternary OSCs.The PCE?Power Conversion Efficiency?of PTB7-Th:[9]CPP:PCBM and PTB7-Th:7+Pyrene:PCBM increased from 7.22%to 8.40%and 7.25%to 7.82%respectively.In order to prove the existence of[9]CPP???PCBM and 7+Pyrene???PCBM supramolecular,Gibbs free energy and binding energy are calculated.The results show that both structures can spontaneously form and exist stably.Experiments indicate that the small circular molecules can form super molecules with PCBM and improve the performance of fullerene OSCs.?2?Investigate the mechanism of small circular molecules in fullerene OSCs.By adding[9]CPP as the third component to the common fullerene system PTB7-Th:PC71BM,the PCE of device was increased from 9.44%to 11.08%.The existence of[9]CPP???PC71BM supramolecular can inhibit the aggregation of fullerene acceptor,make the distribution of active layer to receptor more uniform and facilitate the transport of carriers.In addition,there is ?-? interaction between the supramolecular structure which can promote the charge transfer.The ESP?Electrostatic Potential?of fullerene acceptors increased after the formation of supramolecular with small circular molecules,which increased the potential difference between fullerene acceptors and polymer donors,provided more driving force for exciton dissociation between D/A interfaces,and promoted the generation of free electrons and holes.In this paper,the small circular molecules are added to the classical fullerene binary system,and the performance of the device is improved obviously.The reason of the influence of the supramolecular formed by the ring small molecule and fullerene on the efficiency of the three components is analyzed through the experiment.This study provides a new idea for the selection of ternary material.