Investigation On The Stability Of Perovskite Solar Cells Via Defect Regulation Of The Compositive Materials

Organic-inorganic hybrid perovskite materials have aroused widespread attention among researchers because of their excellent absorption coefficient,long carrier diffusion length,adjustable band gap,solution processing,and flexible perovskite solar cells.At present,the conversion efficiency of perovskite solar cells has reached the certification efficiency of 25.7%.However,oxygen vacancy defects formed during electron transport layer treatment result in the formation of carrier recombination centers.Defects can be formed on polycrystalline perovskite films during the preparation process by the solution method,which becomes the recombination centers of carriers and affects the photoelectric conversion efficiency and stability of devices.Expensive hole transport materials and precious metal electrodes limit the commercialization process of perovskite solar cells.The construction of low-cost printable carbon-based perovskite solar cells is one of the research focuses currently.In this work,the defect passivation of the electron transport layer and perovskite absorption layer was achieved,and the influences of defect passivation on the conversion efficiency and stability of devices were explored based on the construction of a hole-free carbon-based perovskite solar cell,including the following aspects:（1）Defects regulation of metal-oxide electron transport layers（ETLs）such as SnO₂ is an effective strategy for improving the power conversion efficiency（PCE）.However,it is difficult to control the surface defects of SnO₂ using low boiling point solvents,thereby limiting the performance of the perovskite solar cells（PSCs）.We prepared high-quality SnO₂ films by a low-temperature solution method and found that solvent had a noticeable influence on the energy level and oxygen vacancy within SnO₂.Compared to I-SnO₂prepared using isopropanol solvent,D-SnO₂ fabricated using dimethoxyethanol solvent showed excellent photoelectric properties.The perovskite cells based on D-SnO₂exhibited the optimal performance,and the efficiency increased to 20.35%from 18.63%of the device based on I-SnO₂.（2）The electron transport layer is the critical factor affecting the photoelectric conversion efficiency（PCE）and stability of perovskite solar cells.Conventional electron transport layers have problems,low conversion efficiency,and poor stability in the construction of cell devices.Here,we designed a spin coating（SC）-SnO₂/mesoporous structure（MS）-Ti O₂/chemical bath deposition（CBD）-SnO₂ sandwich structure electron transport layer,which is more conducive to the extraction of electrons and improves the short-circuit current of the cell,besides significantly improving the stability of the cell device.The obtained champion hole-conducted-free carbon electrodes device has a PCE of 15.12%;a short-circuit current of 20.45 m A/cm~2,an open-circuit voltage of 1.11 V,and a fill factor of 67%.The cell conversion efficiency remained above 60%of its initial efficiency after60 days in ambient conditions with humidity at 30%.（3）Interfacial engineering has been shown to play a vital role in boosting the performance of perovskite solar cells.Herein,we demonstrate that phenethylammonium iodide（PEAI）,as an interfacial modifier between the MAPb I₃ absorber layer and carbon electrode,can effectively enhance the photoelectric conversion efficiency and stability of hole-conductor-free carbon electrode perovskite devices.The device performance is improved due to the alleviated defects at the perovskite heterojunction and enhanced electron extraction.It is found that compared to devices without PEAI surface passivation,the efficiency of devices with PEAI-coated on the MAPb I₃ film is raised to 17.27%from 11.33%.Furthermore,the champion PSC with PEAI surface passivation,the perovskite layer,exhibited much better stability,which could maintain over 90%of the original PCE after 1500 h storing in ambient air without encapsulation.This work approaches the development of air-processed efficient and stable perovskite solar cells by interface modification for printable hole-conductor-free carbon electrode devices.