Homogeneous And Modified Nickel Oxide Nanoparticles For Printing Flexible Large-area Perovskite Solar Cells And Their Properties

In the past few years,organic-inorganic halide perovskite solar cells have developed rapidly as next-generation photovoltaic devices,benefiting from improvements in photovoltaic efficiency（certified efficiency:25.5%）and stability.However,problems such as environmental stability and large-area printing still restrict its commercial application development.As a typical P-type semiconductor material,nickel oxide（NiO_x）has been widely used in perovskite solar cell devices due to its high stability,low cost,and low-temperature solution printing.Although NiO_x-based perovskite solar cells exhibit high environmental stability,their device efficiencies are still low relative to other systems.The reason is that NiO_x has low intrinsic conductivity,poor interfacial stability,and poor large-area printability,which limits the application of NiO_x as a preferred hole transport material in the commercial development of perovskite solar cells.In view of the many problems existing in NiO_x,this paper has carried out the following work:In order to effectively solve the interfacial instability problem between NiO_x/perovskite,after an in-depth understanding of the interfacial degradation mechanism,a novel method for treating the NiO_x hole transport layer by simple hydriodic acid（HI）soaking during the R2R printing process is proposed.In situ double-sided passivation strategy.Specifically,the trivalent nickel compound on the film surface is reduced to nickel iodide（NiI₂）through the redox reaction of HI,thereby optimizing the interfacial contact and improving the NiO_x work function.At the same time,the interfacial product NiI₂ can coordinate with the lead atoms in the perovskite to form Pb-I bonds,inducing the orderly growth of the perovskite lattice and improving the quality of the crystalline film.Finally,the photoelectric conversion efficiency（PCE）of the optimized flexible devices reached 19.04%（1 cm²）and 16.15%（15 cm²）.And the stability and mechanical properties of flexible devices are also improved.This work provides a deep understanding of NiO_x/perovskite interfacial stability and a printing-compatible method for interface optimization.Poor interfacial contact caused by the inherent agglomeration phenomenon of NiO_x nanoparticles（NPs）remains a bottleneck for the realization of high-performance NiO_x-based perovskite devices.Therefore,the polymer network microprecipitation method was used to synthesize NiO_x NPs with high crystallinity and good dispersion.In addition,the addition of ionic liquid during the dispersion process not only suppressed the secondary aggregation of NiO_x NPs in the precursor solution,but also significantly improved the electrical properties of the colloidal solution.Finally,the best PCE of 20.91%and 19.17%were achieved on the optimized NiO_x-based rigid and flexible perovskite devices（1.01 cm²）,respectively.The reproducibility and stability of the devices are also significantly improved,especially for flexible devices.This strategy offers the possibility of flexible,large-area fabrication of high-quality NiO_xhole transport layers,thereby facilitating the development of stable and efficient perovskite devices.The efficiency of NiO_x-based formal perovskite devices has exceeded 19%and has good long-term stability,which also shows the broad application prospects of NiO_xin formal devices.To achieve high-performance NiO_x-based devices,the primary task is to develop high-quality NiO_x inks.In this paper,a stable dispersion of NiO_x ink was prepared based on the surface modification of F4TCNQ molecules,and finally a PCE of 16.81%was obtained on the de-printed device.