Effect Of Interface Engineering On Carrier Transport Performance Of Perovskite Solar Cells

With the outbreak of the information age,people’s demand for energy is increasing.The depletion of fossil energy and its damage to the human living environment have made it increasingly urgent for humans to explore and develop new clean energy sources.As a clean energy source,sunlight is inexhaustible,and it has become the focus of researchers around the world.The development of solar energy can be an important pillar to solve the energy crisis.Perovskite solar cells（PSCs）have developed rapidly since their introduction.Perovskite materials have advantages such as a wider bandgap adjustment range,a carrier diffusion length greater than 1 μm,and excellent light absorption coefficients,making their photoelectric conversion efficiency to 25.2% in ten years.However,there are still many problems: there are many defects in organic-inorganic hybrid materials,and the effective transport of photo-generated electrons and photo-generated holes needs to be further improved.This article mainly adjusts the electron transport layer（ETL）energy level structure through interface engineering to improve the carrier transport properties at the interface;promotes the growth of perovskite films by optimizing the TiO₂ film and reduces the non-radiative recombination centers;interface modifies the passivated calcium Defects of titanium ore film,improve film quality,improve carrier transport performance,and prepare high-performance and stable PSCs.The main conclusions are as follows:（1）A method for modifying the interface between the perovskite layer and ETL with ammonium fluoride（NH₄F）was proposed.After the TiO₂ film is modified with NH₄F,the interface defects of ETL and perovskite are alleviated and passivated,the carrier recombination is reduced,and the electron extraction and injection capabilities are increased.Therefore,in an environment with a relative humidity of 20%,the planar PSCs modified with the optimal NH₄F concentration can maintain an initial efficiency of more than 95% within 32 days and obtain a champion efficiency of 20.47%.Under the same conditions,the efficiency of the control device is only 18.59%.（2）ETL is one of the reasons affecting the quality of perovskite films.We use LiBF₄ to modify TiO₂ to reduce the roughness of ETL and surface Gibbs free energy,improve the crystallinity of perovskite,and reduce the number of carrier recombination center;Li⁺ provides holes at the interface of perovskite and ETL,which is conducive to the efficient transfer of electrons and reduces interface loss.Based on this,a cell assembled with a LiBF₄ modified ETL surface with a concentration of 50 mM has a higher open circuit voltage and fill factor.Compared with the 18.56% PCE of a control device before LiBF₄ treatment,the highest efficiency is 20.42%.（3）The potassium perfluorooctane sulfonate colloidal spin-coated on a perovskite thin film is grown uniformly perovskite grain boundaries.A series of characterization methods proved that potassium perfluorooctane sulfonate deactivated the defects of the perovskite film;reduced the non-radiative recombination of carriers;improved the energy level structure of the perovskite film;and improved the carriers The transmission performance is reduced;the reverse saturation current density is reduced,and the open circuit voltage of the device is increased.When the colloidal concentration was 0.2 mg/mL,we obtained the best device with a photoelectric conversion efficiency of 20.64%,and the corresponding V_OC,J_SC,and FF were 1.16 V,22.95 mA·cm^-2,and 77.64%.