| Due to their excellent optoelectronic semiconductor properties,such as suitable direct band gap,high absorption coefficient,excellent carrier transport properties,high defect tolerance and relative permittivity,organic-inorganic hybrid perovskite materials have been widely applicated in the fabrication of optoelectronic devices;particularly,they present great potential in the field of perovskite photovoltaic applications.In just ten years,the traditional structure(n-i-p)of perovskite solar cells(PSCs)have an increasing power-conversion-efficiency(PCE)from 3.8% to 25.8%(certified PCE of25.7% by NREL).Inorganic nickel oxide(NiOx)based planar inverted(p-i-n)PSCs present several advantages,such as high stability,ease fabrication process and suitable for the preparation and industrialization of large-area photovoltaic modules.Such good characteristics are attributed to excellent properties of NiOx,such as high transparency,good chemical stability and cost-effectiveness.Thus,NiOx has been considered as one of the most promising p-type inorganic hole transport materials.However,NiOx based inverted PSCs still have shown low PCEs attributed to surface and interface defects,and inhomogeneity of perovskite films with many pin-holes and random growth of crystals.Such defects induce unbalance charge(hole/electron)concentration,which several restrict further improvement of solar cell performance and stability.Therefore,the goal of this thesis is to improve perovskite film quality by introducing effective additives into perovskite precursors.Finally,highly efficient and stable NiOx based inverted PSCs are fabricated.The specific work content is as follows:1.Passivation of perovskite bulk and interface defects by introducing OAm ligandsThe additive of OAmI was introduced into tri-halide perovskite precursor,We found that OAm ligands can not only assist the growth of perovskite crystals with vertical orientation,but also form 2D@3D perovskite heterojunction.In addition,when the 2D@3D perovskite heterojunction film is post-treated with PEA ligands,a2D@3D/2D perovskite heterostructure is further formed.As a result,OAm and PEA ligands can assist the growth perovskite crystals and passivate defects at perovskite bulk,surface and buried interfaces,leading to reduced non-radiative recombination and trap density.Therefore,defects at bulk and heterointerface of triple-halide perovskites can be remarkably passivated,leading to an improved efficiency over 20% without any J-V hysteresis in NiOx-based inverted PSCs.This work provides new ideas for the use of long-chain alkylamine ligands(LALs)as an ideal passivator to inhibit the development of perovskite interface defects and body defects to high-performance PSCs.2.Introduction of OAmI and F4-TCNQ additives into perovskite precursor solutionExcept for the introduction of the additive OAmI into the perovskite precursor solution,another additive,F4-TCNQ,was further added.F4-TCNQ is a P-type organic semiconductor material,which is often used as a hole transport layer with excellent carrier extraction and hole transport capabilities.With the action of two additives,perovskite bulk and interface defects can be effectively passivated,and band structure is effectively regulated,resulting in better charge transport balance.As a result,NiOx based inverted PSCs based on the perovskite composite layer incorporated two additives show a PCE of up to 21.8%,and better stability. |
