SnO2表面卤化提高钙钛矿太阳能电池光伏性能

钙钛矿太阳能电池(PSCs)成为近几年来迅速发展的新型太阳能电池,其中将SnO₂纳米粒子层用作电子传输层(ETL)的钙钛矿太阳能电池器件得到了广泛的关注。SnO₂有着更低的制备温度,使其具备应用于柔性器件的潜力,但与钙钛矿层能级不匹配等问题限制着其发展。而在界面处加入钝化层,尤其是表面卤化的方法或可解决这一问题。本文综合研究了SnO₂表面卤化对钙钛矿太阳能电池光伏性能的影响,选用四丁基氯化铵(TBAC)、四丁基溴化铵(TBAB)和四丁基碘化铵(TBAI)三种钝化材料对SnO₂表面进行钝化处理,并对钝化材料溶液进行了浓度梯度研究。通过材料形貌、结构和光学性能表征以及电池器件性能测试分析等方法,证明了SnO₂表面卤化可提高钙钛矿层的质量和PSCs光伏性能,并从器件内部电荷传输动力学等角度解释了器件性能改善的原因。为进一步说明其性能改善的机理,采用基于密度泛函理论(DFT)的第一性原理计算方法对材料表面性质进行了深入研究,从能量、结构、电荷密度、态密度、功函数等角度解释了表面卤化提高SnO₂/钙钛矿界面处电子传输特性的原因。实验和理论计算均表明TBAC对于SnO₂具有较好的钝化效果,并随着溶液浓度的提升钝化作用越明显。SnO₂表面卤化作用的深入研究不仅对提高电池器件性能具有实际意义,还能够帮助理解太阳能电池界面现象,为界面改性提供新的研究思路。

SnO2Surface Halogenation to Improve Photovoltaic Performance of Perovskite Solar Cells

Perovskite solar cells(PSCs)have recently become one of the fastest-growing research fields.Furthermore,the PSCs that have a SnO₂nanoparticle layer as an electron transport layer(ETL)have received extensive attention.The SnO₂-ETL layer can be prepared at a low temperature,which makes it suitable for flexible device development.However,the energy levels of the SnO₂layer do not sufficiently match the energy levels of the perovskite lightabsorbing layer,which largely affects the charge carrier extraction and reduces the open current–voltage(Voc)of PSCs.Additionally,the interface between the ETL and perovskite layer always has defects,which cause charge recombination and affect the power conversion efficiency(PCE)of PSCs.Therefore,the interfacial engineering at the SnO₂/perovskite layer is crucial to address these issues.Researchers are looking for suitable passivation materials that could align the energy band and decrease the defect density.Halide materials,such as KCl and NH₄Cl,are promising solutions to solve these problems.However,the preparation process has to be explored,and the mechanism of halide ions at the interface is unclear.This study investigates the effects of SnO₂surface halogenation on the photovoltaic performance of PSCs in depth.The SnO₂surface was passivated using tetrabutylammonium chloride(TBAC),tetrabutylammonium bromide(TBAB),and tetrabutylammonium iodide(TBAI)and the concentration gradient of the passivation solution was studied.Extensive characterization of the perovskite layers and PSC devices demonstrated the positive effects of SnO₂surface halogenation on the SnO₂/perovskite interfacial properties.The causes of improved performance of the interfacialengineered devices were studied using charge carrier dynamics.Interfacial engineering was further investigated by performing first-principles calculations based on density functional theory(DFT)to determine the energy,structure,charge density,density of states,work function,etc.Experiments and theoretical calculations proved that TBAC could be an optimal passivation material for the SnO₂surface.Furthermore,the passivation effect became more apparent with the increase in solution concentration.TBAC could promote perovskite crystal growth,decrease defects at the interface,and increase the internal recombination resistance.Consequently,the photovoltaic performance of PSCs was improved.The halide ions on the SnO₂surface could interact with Sn atoms,which increase the charge density and achieves highefficiency charge extraction.This work shows the significance of improving the photovoltaic performance of PSCs along with providing physical principles for the interfacial engineering of PSCs toward achieving high efficiency.