Application Of Small Organic Molecules In Perovskite Solar Cells

With the increase of population and social development,human beings have an increasing demand for various resources.The decrease of traditional fossil energy and the environmental pollution caused by relatively primitive consumption methods force human beings to seek sustainable,clean and safe new energy.The inexhaustible advantages of solar energy make solar cells attract the attention of researchers.Among many types of photovoltaic materials,organic-inorganic hybrid perovskite,as a direct bandgap material,It has many advantages such as adjustable band gap,high optical absorption coefficient,low exciton binding energy and crystallization energy,long carrier diffusion length and high carrier mobility,getting more and more attention.After ten years of development of solid-state single-heterojunction perovskite solar cells,it is highest photoelectric conversion efficiency has increased from 3.8%to 25.7%,and the value is getting closer and closer to the theoretical limit of Shockley-Queisser.However,in the development of perovskite solar cells,there are always some problems:for example,the defects generated by the perovskite crystal itself,and the stability brought by the low sensitivity of perovskite to moisture,oxygen,light,high temperature,etc.based on these problem,researchers have developed methods such as additive engineering,solvent engineering,component engineering,and interface engineering to improve.This paper mainly optimizes organic-inorganic hybrid perovskite solar cells from defect passivation and interface modification.This paper is mainly divided into the following parts:（1）The development history,basic principle,structure and research status of each layer of perovskite solar cells are briefly described.Classic examples of passivation include Lewis acids and bases,fullerene derivatives,polymers,organic ammonium salts,ionic liquids,inorganic salts,etc.In addition,the research ideas of this article are proposed.（2）In order to improve the photoelectric conversion efficiency and stability of perovskite solar cells,In this paper,FA_0.9Cs_0.07MA_0.03Pb(I_0.92Br_0.08)₃ organic-inorganic hybrid perovskite is used as the photoactive layer,and 1,3-dihydroxypropan-2-one（DHA）is used as a surface passivator to modify the interface.Fabrication of n-i-p-type perovskite solar cells with the structure of FTO/compact-Ti O₂/Sn O₂/Perovskite/DHA/Spiro-OMe TAD/Au by a one-step solution method,firstly,we screened the concentration of DHA passivator and determined that the best photoelectric performance can be achieved at the concentration of 0.4mg/m L,making the average fill factor,Open circuit voltage,Photoelectric conversion efficiency were higher than the control group,and the highest photoelectric conversion efficiency reached 23.26%.The perovskite crystal structure was characterized by SEM,XRD,It shows that the experimental group perovskite has higher crystal quality.the interaction between DHA and perovskite films was determined by FTIR,and the optical properties and perovskite films were characterized by UV-vis,EQE,PL,TRPL,etc.The carrier transport was analyzed,and the perovskite solar cells were characterized by SCLC,Nyquist curve,capacitance-voltage curve,ideality factor calculation,and J-V characteristic curve.The results show that the uncoordinated Pb²⁺and FA⁺defects on the perovskite surface are passivated after DHA passivation treatment,the defect density of perovskite is reduced from 7.26×10¹⁶ cm^-3 to 4.72×10¹⁶ cm^-3,and the ideality factor is reduced from 1.73 k T/q decreased to 1.38k T/q,the reduction of defects improved the non-radiative recombination of carriers at the interface,and the average lifetime of carriers increased from 85.65 ns to 163.74 ns.The Nyquist curve also proved that the interface The increase in the non-radiative recombination resistance of the carriers.In addition to the improvement in optoelectronic properties,DHA also improves the air and thermal stability of perovskite solar cells.