Constructing High-Performance Organic Solar Cells Based On Interfacial Modulation And Ternary Strategies

With the fast development of today’s economy and technology,the demand for energy is increasing.In the face of the gradual decline of fossil energy sources（coal,oil,natural gas）and the environmental pollution caused by their consumption,it is urgent to develop sustainable and environmentally friendly energy sources.Organic solar cells（OSCs）have attracted a great deal of attention due to their light weight,low cost,flexibility,ease of roll-to-roll processing and manufacturing,and their bright future in building integration or portable panels.However,the power conversion efficiency（PCE）of OSCs is still low compared to that of inorganic silicon solar cells and the emerging perovskite solar cells,and improving the PCE of OSCs is still the focus of current research.This thesis focuses on the main mechanisms of using natural biomaterials for interfacial modification of Zn O,thereby improving the performance of inverted OSCs（IOSCs）,and the main mechanisms of using ternary strategies to improve the performance of traditional OSCs,as follows:1.The application of zinc oxide（Zn O）as a classical electron transport layer（ETL）material in OSCs still suffers from a preparation process that is prone to surface defects,energy levels that are not easily adjustable,and poor organic/inorganic（active layer and Zn O）compatibility.To solve these problems,this research has effectively improved the performance of IOSCs with PM6:Y6 as the active layer by introducing the green natural biomaterial histidine to modify indium tin oxide（ITO）or Zn O.With the histidine modification,the ITO and ITO/Zn O films have a smoother surface morphology,better compatibility with the active layer and better energy level matching with the acceptor,facilitating carrier transport and inhibiting carrier recombination in IOSCs with histidine or Zn O/histidine as the ETL.The PCE of the IOSC with histidine and Zn O/histidine as the ETL was improved to 12.10%and 16.02%respectively,and the short circuit current density(J_SC),open circuit voltage(V_OC)and fill factor（FF）were all improved.Also,the IOSCs with histidine or Zn O/histidine as the ETL have higher stability compared to Zn O-based IOSCs.This research has shown that the natural biomaterial histidine can be used as an ETL to effectively modify ITO or ITO/Zn O,thereby improving the efficiency of IOSCs.2.The narrow absorption spectra of single organic photovoltaic materials and the limitations of their weak absorption of photons limit the efficiency of traditional binary OSCs for photon utilisation.In this study,the ternary bulk heterojunction（BHJ）OSCs and layer-by-layer（Lb L）OSCs were constructed by using the polymer donor PM6 and the non-fullerene acceptor L8-BO as the main systems and the fullerene acceptor PC71 BM as the third component.With the introduction of PC71 BM as the third component,the JSC and FF of the three components were simultaneously improved,with the PCE of the BHJ OSCs increasing from 17.10% to 18.02% and the PCE of the Lb L OSCs increasing from 17.20% to 18.20%.With the introduction of PC71 BM as the third component,the efficiency of photon utilisation can be effectively improved,a smoother active layer surface morphology can be obtained,and the molecular orientation and molecular crystallinity in the active layer can be effectively improved,which is conducive to the dissociation of excitons and carrier transport.This study shows that the introduction of the fullerene acceptor PC71 BM as a third component into the PM6:L8-BO system can well improve the performance of the traditional OSCs.At the same time,the ternary OSCs obtained with the Lb L treatment show great potential for development.