A Research Of High Efficiency Organic Solar Cells Based On Interface Modification Strategy

Organic solar cells（OSCs）are solar cells that use organic material as photovoltaic materials.They can be processed in solution,with the advantages of being lightweight,flexible,and semitransparent,have been taken as a potential substitute for conventional silicon solar cells.In OSCs,the contact interface between electrode and active layer is significant for device performance.However,current research of interface modification pay more attention to modification towards electrode,such as passivating metal oxide transport layer,work function modification and so on.The interaction between the interface layer and the active layer is rarely mentioned.Therefore,in thesis,we use a new hydrogen bond induced interlayer modification strategy to improves the performance of the inverted OSCs.It can induce hydrogen bond between active layer and interlayer which optimizes the vertical phase separation improving charge transportation.Finally inverted OSCs based on PM6:Y6 with high efficiency and stability were fabricated.The main work and conclusions of this paper are summarized as follows:1.Using hydrogen-bonds-induced self-assembled materials as the interlayer to regulate the performance of the OSCs.In thesis,three kinds of hydrogen-bonds-induced self-assembled materials 1H-benzimidazole-5-carboxylic acid（2N-SAM）,6-aminonicotinic acid（NA-SAM）and 5-methoxyindole-3-acetic acid（MA-SAM）are used as interlayer and high-efficiency OSCs were fabricated based on PM6:Y6.In these materials,2N-SAM is the most representative one.Compared with pristine Zn O-based OSCs,the short-circuit current density(J_SC)of 2N-SAM-based OSCs increased from24.73 m A/cm~2 to 27.08 m A/cm~2,and the power conversion efficiency（PCE）increased from 14.5%to 16.03%.The research shows that the carboxylic acid group of 2N-SAM make a directional arrangement of 2N-SAM on the surface of Zn O and Hydrogen bonds are formed between the N–H bonds of 2N-SAM and the F atom of acceptor Y6 achieving a vertical phase separation in the active layer of the acceptor enrichment at the cathode and improving transportation of electrons.Finally,the electron collection efficiency and the stability of the interface are improved.The interface layer hydrogen bonds effectively improve the charge transport and reduce the trap assisted recombination caused by the interface defect,finally improves the exciton dissociation and transport efficiency.2.We further explored the possibility of using self-assembled materials as hole-selective interlayer,The surface work function of indium tin oxide（ITO）can be adjusted by self-assembled materials to achieve the effect of blocking electrons and transmitting holes,and so that indium tin oxide（ITO）can be used as anode.Through experiment,It is found that the acidity of anchoring groups of self-assembled materials is one of the key factors affecting the performance of devices.In addition,we also tried to use the concept of"molecular lock"in the active layer and use N-H group to form hydrogen bonds in the active layer.Compared with the hydrogen bond formed by hydroxyl group,the influence of the strength of hydrogen bond on the performance of the device is studied.In thesis,a series of self-assembled materials that can induce interface hydrogen bonds forming between active layer and interlayer are studied,which proves the function and feasibility of interlayer hydrogen bonds,providing a new idea for interface layer modification.