Research On Interfacial Regulation And Photovoltaic Performance Of P-i-n Perovskite Solar Cells

In recent years,perovskite solar cells（PVSCs）have gradually developed the most promising solar cell technology in the photovoltaic field because of their low cost and high efficiency.The certification power conversion efficiency（PCE）of PVSCs has reached 25.5%,which can compare with commercial silicon solar cells.To obtain high-performance PVSCs devices,numerous research studies have focused on regulating the chemical composition of perovskite and optimizing the charge transporting layers,yet the interfacial mismatch between perovskite and charge transporting layers is a nonnegligible issue that dominates the efficiency and stability of corresponding devices.Nickel oxide（NiO_x）nanocrystals as a promising stable hole transporting layer（HTL）in inverted p-i-n PVSCs are less prone to hysteresis and work well with flexible or tandem architectures.However,the easy-agglomeration phenomenon of NiO_x nanoparticles（NPs）and adverse interfacial reaction are still the bottleneck for achieving high-performance devices.Therefore,it is urge to solve these issues for performance enhancement and commercialization application of NiO_x-based PVSCs.In NiO_x-based PVSCs,the detrimental interfacial reaction occurs between Ni³⁺of NiO_xinterface and A-site cation salts.This adverse redox reaction will form Pb I₂-rich hole extraction barriers at NiO_x/perovskite interface,which is likely to limit hole mobility,resulting in device open-circuit voltage(V_oc)loss.Moreover,inconsistent thermal expansion of lattice units in NiO_x and perovskite results in tensile strain,prejudicing the microstructure and accelerating the degradation of perovskite.Therefore,interfacial lattice mismatch and adverse reaction are the key issues hindering the development of NiO_x-based inverted PVSCs.Herein,a p-chlorobenzenesulfonic acid（CBSA）self-assembled small-molecules（SASMs）,is adopted to anchor NiO_x and perovskite crystals to endow dual-passivation.The chlorine（-Cl）terminal of SASMs can provide growth sites for perovskite,leading to interfacial strain release.Meanwhile,the sulfonic acid（-SO₃H）group from SASMs can passivate surface defects of NiO_x conducing to charge carrier extraction.In addition,the self-assembled layer inhibits the adverse interfacial reaction by preventing NiO_x contact with perovskite.Therefore,the NiO_x/CBSA-based PVSCs obtain the champion PCE of 21.8%.Satisfactorily,the unencapsulated devices can retain above 80%of their initial PCE values after storing in N₂ for 3000 h,in air with relative humidity of 50-70%for 1000 h and heating at 85°C for 800 h,respectively.Moreover,the inherent easy-agglomeration phenomenon of NiO_x NPs is the key factor for obtaining large-area perovskite films.Herein,a general strategy to synthesize NiO_x NPs with high crystallinity and good dispersibility by introducing a NiO_x growth template.The imidazolium cation（C_nMIm⁺）with different alkyl chain lengths can be adsorbed on the surface of O^2-in NiO_x via electrostatic force.Moreover,the hydrogen bond is formed between the H atom of N-H for the imidazole ring and the oxygen atom on O-Ni.Then,the hydrogen bonding network is extended which becomes a template for the growth of NiO_x.Furthermore,the presence of ionic liquid not only inhibits the secondary aggregation of NiO_x NPs during the dispersion process,but also act as the growth inducement platform for subsequent perovskite growth and enhance the crystal quality of perovskite.Therefore,the PVSCs based on the NiO_x-ILs achieve the champion PCE of 21.7%.Overall,this strategy provides the possibility for large-area and high-quality NiO_x-based PVSCs.