Preparation Of High Efficiency And Stable Perovskite Solar Cells Based On Additive Strategy And Interface Modification

Perovskite solar cells（PerSCs）represent a cutting-edge photovoltaic technology that boasts advantages such as lightweight construction,exceptional light capture capability,and extended carrier diffusion distances.In recent years,these qualities have propelled PerSCs to the forefront of global research on innovative energy devices.The photoelectric conversion efficiency of PerSCs has experienced significant growth,from an initial 3.8%to a current rate of 25.7%.Device performance is oriented towards the industrialization of perovskite photovoltaic technology,and synchronous improvement of the PCE and stability of PerSCs is crucial to the development of this technology.Due to the polycrystalline nature of perovskite thin films produced through solution methods,a substantial number of grain boundaries exist between the crystals.Within these thin films,grain boundary ions migrate more rapidly than ions at other sites,rendering them particularly susceptible to water and oxygen attacks.Consequently,grain boundary defects can considerably undermine the operational stability of PerSCs.To counteract these defects,crystallization regulation and interface modification have proven effective in mitigating grain boundary issues,which is crucial for enhancing the overall performance of PerSCs.This thesis aims to develop stable and efficient perovskite solar cells by reducing non-radiative recombination,fortifying the built-in electric field,and protecting against water and oxygen corrosion through crystal regulation or interface modification.The primary work and innovative contributions are as follows:（1）During the preparation of PerSCs,the quality of the active layer thin film significantly impacts device performance.Excessive grain boundaries and numerous defects can result in suboptimal device performance.In this study,a novel active layer modification strategy employing oximic acid-based additives is proposed for the first time:BHA is introduced into the Pb I₂precursor solution to regulate the growth process of FA_0.92MA_0.08Pb I₃perovskite thin films.It was discovered that incorporating BHA additive not only passivated the perovskite’s internal defects but also regulated the crystallization process,leading to a perovskite thin film with a low defect density of states and large grain size.Simultaneously,BHA effectively inhibits non-radiative recombination within the film,enhancing the internal electric field strength and boosting the photoelectric conversion efficiency of BHA-modified PerSCs to 23.21%.In addition,after continuous heating at80°C for 240 hours,the PCE of the BHA modified device maintained 58.2%of its initial value.After being placed in a humidity atmosphere of 40±5%for360 hours,the PCE value of the BHA modified device still maintained 81.4%of the initial PCE.This study highlights the potential of using the oximic acid based additive BHA as an additive to improve device efficiency and stability.However,there is still significant room for improvement in its ability to enhance the thermal stability of devices,so it is necessary to further develop better performance oxime acid based additives.（2）To further enhance the coordination ability of oximic acid-based additives,EHA additives with additional coordination groups are investigated,combining systematic theoretical calculations and experimental research.It is concluded that EHA can connect Pb I₂clusters in Pb I₂precursor solutions,reduce nucleation sites during perovskite growth,lower the Gibbs free energy barrier for nucleation,and form high-quality perovskite films.Moreover,by connecting grains and filling grain boundaries,EHA promotes charge transfer and extraction processes within the film,extends the carrier lifetime of the active layer,strengthens the built-in electric field,and increases the power conversion efficiency to 24.10%.Thanks to the regulatory effect on the perovskite crystallization process and the inhibition of internal defects in the film,modified PerSCs exhibit excellent stability.After storing in N₂atmosphere for 2000 hours,the EHA modified device can still maintain an initial efficiency of 90%.After heating at 80°C for 200 hours,the PCE value of EHA modified devices can still maintain 76.5%.After being placed in an air atmosphere with a relative humidity of 40±5%for 500 hours,the PCE value of the EHA device still maintained 91.7%of the initial PCE.This chapter provides important insights into defect passivation and growth regulation of perovskite thin films,which is expected to simultaneously address the efficiency and operational stability issues of PerSCs.（3）In an effort to enhance the performance of inverted PerSCs,the perovskite upper interface was modified.Photoinduced crosslinking materials UMA and BMA were spin-coated onto the perovskite’s upper surface,and in-situ crosslinking was completed through sunlight irradiation.Systematic studies reveal that the photoinduced crosslinked layer effectively passivates interface defects,inhibits non-radiative recombination,and strengthens the built-in electric field.According to DFT simulation calculations and experimental results,due to theπ-πinteraction between BMA molecules,BMA can be more densely arranged on the perovskite’s upper surface.Consequently,compared to UMA,BMA demonstrates a stronger passivation effect on defects in perovskite films,protecting the films and enhancing their resistance to water and oxygen attack.Ultimately,the PCE of BMA modified devices increased to 24.45%,and the PCE of UMA modified devices increased to 23.72%.After heating at 80°C for 240 hours,the PCE of BMA modified devices remained at 92.3%of the initial value,while the PCE of UMA modified devices decreased to 87.6%,and the PCE of standard devices declined to 42.9%.After storing in a relative humidity atmosphere of 40±5%for 360 hours,the PCE of the standard device decreased to 40.2%of the initial value,while the PCE of the BMA modified device remained at 93.7%of the initial value,and the PCE of the UMA modified device decreased to 90.5%.This study provides beneficial insights for addressing the efficiency and stability issues of PerSCs through interface modification of perovskite thin films.