Application Of Solution-processable Interface Materials In Novel Solar Cells

The rapid development of organic solar cells(OSCs),driven by the design and synthesis of new active layer materials and the device process,the efficiency of single-junction cells has exceeded 16%.As the main component of OSCs,interface materials have a significant impact on the improvement of device efficiency.The interface material that matches the active layer determines the built-in electric field of the device,the efficiency of charge collection,the utilization of incident light,the morphology of the active layer,and the orientation of molecular crystals.These factors all affect the efficiency of this device,and how to maximize the photoelectric conversion efficiency(PCE)of the active layer requires research on the influence of interface materials on the active layer.Therefore,in this paper,the effect of the interface material processed by the solution on the active layer is studied,and the function of the interface material is adjusted so that the efficiency of the device reaches an optimal value.This article focuses on the effects of interface materials on device performance.The main content is as follows:1)We use the anode interface material WOx instead of PEDOT:PSS,and the cathode interface material Hf(Acac)4 instead of low work function metal Ca.In the PBDB-T:IT-M system,the influence of interface materials on the utilization of incident light was studied.The refractive index and extinction coefficient of the interface of each layer were measured using ellipsoidal instrument.It was found that WOx and Hf(Acac)4 have very low extinction coefficients.The simulation of transmission matrix shows that the optical electric field intensity of the device with WOx-Hf(Acac)4 structure is greater than that of PEDOT:PSS-Ca.The simulated exciton generation map also shows that the WOx-Hf(Acac)4 structure has a better exciton generation range.Through the synergy of WOx and Hf(Acac)4,the short-circuit current(Jsc)of the device is increased from 15.07 mA cm-2 of PEDOT:PSS-Ca to 16.65 mA cm-2 which makes the PCE of the device reach 10.60%.2)We introduced Nafion to adjust the surface energy(SFE)of PEDOT:PSS.The SFE of PEDOT:PSS and PEDOT:PSS-Nafion was calculated by contact angle measurement and Owens formula.After adding Nafion,the SFE of PEDOT:PSS decreased,which greatly affected the distribution of donor PBDB-TCl and acceptor IT-4F in the photoactive layer,indicating that low SFE is conducive to donor enrichment at the anode.By precisely adjusting the ratio of Nafion to PEDOT:PSS,the PCE of the optimized device has reached 14.12%,which is greatly improved compared to the pure PEDOT:PSS based device(13.01%).AFM,TEM,and EDS tests confirmed that SFE reduced enrichment of the anode-side donor.EIS and IMVS studies show that the ideal donor-acceptor distribution induced by the PEDOT:PSS-Nafion interface layer promotes charge transfer and reduces the resistance of the device,thereby greatly improving JSC and FF.All these results show that adjusting the SFE of PEDOT:PSS by Nafion mixing is an effective method to improve the performance of OSCs.