Study On Charge Transport In Organic Solar Cells Based On Polymer:Non-Fullerene Blends

Solar energy as a green and clean energy,has great potential for development.Organic solar cells have become a research hotspot in recent years due to their outstanding advantages such as low processing costs and diverse structures.As research progresses,polymer: non-fullerenes organic solar cells with non-fullerenes as the acceptor material exhibit high photoelectric conversion efficiency.However,some of the working mechanisms of this system are still unclear and the charge transport laws still need to be further explored.In response to the above,this paper examines the following:Firstly,the J-V characteristics of PM6:Y6 blends hole-only and electron-only devices based on polymer: non-fullerene systems are investigated using an improved extended Gaussian disorder model(IEGDM)and an extended correlated disorder model(ECDM)combined with a non-uniform discretization numerical calculation method,respectively.Comparison of the obtained parameters leads to the conclusion that the site spacing obtained using IEGDM is more realistic than that obtained using ECDM.Therefore,the IEGDM model is more suitable for the study of PM6:Y6blends than ECDM,where the site-energy spatial correlation is non-existent or negligible.Then,the effect of the boundary carrier concentration of the device on the J-V characteristics and the distribution of carrier concentration and electric field intensity in the organic active layer are further calculated and analyzed.Secondly,the effect of diffusion on charge transport in polymer: non-fullerene blends(PM6:Y6)is investigated.The J-V characteristics of PM6:Y6 hole-only and electron-only devices were analyzed using the extended Gaussian disorder model(EGDM),which is widely accepted in the research field,considering diffusion and neglecting diffusion,respectively.It is concluded that the effect of diffusion is significant in the low voltage range,while it can be neglected in the high voltage range.The conclusions are verified with another polymer: non-fullerene ternary system(PBDB-T:IEICO-4F:PCBM)with better properties.Finally,for carrier transport not only nearest-neighbour hopping(nn H)but also variable-range hopping(VRH)are considered,the concept of effective temperature is introduced.According to this theory,it is improved on the basis of EGDM model.The model is applied to the studied polymer: non-fullerene blend PM6:Y6 hole-only and electron-only devices and has some superiority compared to the initial model(EGDM),confirming that the model does have some applicability.