| Organic solar cells(OSCs)are considered to be the next generation of promising new energy cell technology.OSCs stand out among many new energy photovoltaic technologies due to their unique advantages,such as low cost,solution processability,and the possibility of multi-functional applications for semi-transparent or flexible devices.As the key part of photoelectric conversion,the active layer plays a crucial role in the working process of the device.The microstructure of the active layer seriously affects the power conversion efficiency(PCE)of the devices.Appropriate morphology can promote the procedure of dissociation,transport,and collection,thereby obtaining an outstanding PCE.In this paper,ternary strategies and solvent engineering were used to modulate the active layer morphology.Following,the charge recombination,energy loss,and device performance were optimized.We systematically studied the effect of modulating the morphology of the active layer on the photovoltaic performance of the devices.The main research results are as follows:(1)Ternary OSCs were constructed by introducing a well-compatible non-fullerene acceptor MOIT-M into the PM6:BTP-eC9 binary system.The result shows that MOIT-M possesses complementary absorption with PM6:BTP-eC9 blend and constitutes a cascade energy structure,which is beneficial for improving the utilization of the solar spectrum and promoting exciton dissociation and charge transport.At the same time,due to the good compatibility of two acceptors,MOIT-M tends to mix with BTP-eC9.This well-mixed phase optimizes the active layer morphology,resulting in high and balanced mobility with reduced charge recombination.Notably,the incorporation of MOIT-M suppresses the non-radiative recombination,leading to reduced non-radiative energy losses(ΔEnr).The optimized ternary OSCs possess a small ΔEnr of 0.21 eV,Voc of 0.87 V,FF of 77.3%,and Jsc of 27.4 mA/cm2,resulting in a significantly improved PCE of 18.5%,while PM6:BTP-eC9 binary device exhibits a PCE of 17.4%with a ΔEnr of 0.24 eV.This work provides an efficient method that synergistically minimizes non-radiative energy loss and optimizes morphology.(2)Limited by solubility and poor morphology,the efficiencies of OSCs processed with environment-friendly solvents are still relatively low.Based on the PM7-TTz50:BTP-BO-4F binary system,the effect of modulating the processing solvent on the morphology of the active layer was investigated.The solubility and boiling point of the solvents affect the miscibility of the material and the film formation process.Due to the higher boiling point and lower solubility of Tol,the pre-aggregation properties of the materials in solution are enhanced and more time is provided during the volatilization process for the wet film to further aggregate.Therefore,the Tol-processed blend film obtains higher crystallinity and ordered packing,while obtaining a relatively larger donor and acceptor phase,which is beneficial to suppressing charge recombination and improving carrier mobility.Ultimately,the device processed with Tol achieves a PCE of 18.0%with Voc of 0.87 V,FF of 76.7%,and Jsc of 26.9 mA/cm2,which is about 13%higher than 15.8%of CF-processed devices.This is one of the highest efficiencies when processed with environmentally friendly solvents. |
PDF Full Text Request