Perovskite solar cells (PSCs) are currently the most exciting solar photovoltaic technologies for future deployment. A conventional PSC device structure typically employs a titanium dioxide (TiO₂) electron transport layer. However, the low electrical conductivity of TiO₂ is an obstacle to PSC efficiency enhancement. In this paper, we report on the conductivity enhancement of TiO₂ by tantalum (Ta) doping and its effect on improving the device performance. In contrast to commonly used mesoporous TiO₂, our work used a planar PSC device structure based on a compact TiO₂ layer with the device structure being: FTO/compact-TiO₂/CH₃NH₃PbI₃/P3HT/Ag. Photovoltaic measurements show that Ta doping of compact TiO₂ results in an improvement in the fill factor (FF) of the devices due to a decrease in the series resistance (R_s), attributed to improved charge transport and an increase in the shunt resistance (R_sh), due to reduced leakage paths. These changes were examined using Kelvin probe force microscopy (KPFM) which indicated that the Fermi level of TiO₂ shifts downward upon Ta doping providing driving force for the electron transfer from the perovskite LUMO to the TiO₂ conduction band resulting in higher current density. Furthermore, impedance spectroscopy analysis of the devices suggests a decrease in the charge transfer resistance with Ta-doping and an increase in R_sh due to the higher recombination resistance of doped films. PSC devices with Ta doping of 3.0% led to a 40% improvement in the overall efficiency as compared to un-doped TiO₂ with the best device showing a power conversion efficiency of ca. 9.94%.

中文翻译：

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钽掺杂在TiO ₂致密层中对无平面螺线体-OMeTAD的钙钛矿太阳能电池性能的影响†

钙钛矿太阳能电池（PSC）是目前最令人激动的未来太阳能光伏技术。传统的PSC器件结构通常采用二氧化钛（TiO ₂）电子传输层。然而，TiO ₂的低电导率是PSC效率提高的障碍。在本文中，我们报道了通过钽（Ta）掺杂提高TiO ₂的电导率及其对改善器件性能的影响。与常用的介孔TiO _2相比，我们的工作使用了基于致密TiO ₂层的平面PSC器件结构，该器件结构为：FTO / compact-TiO ₂ / CH ₃ NH ₃ PbI₃ / P3HT / Ag。光伏测量表明，由于串联电阻（ R _s）的降低，致密的TiO _2的Ta掺杂导致了器件的填充因子（FF）的改善，这归因于电荷传输的改善和分流电阻的增加（ R _sh），因为减少了泄漏路径。使用开尔文探针力显微镜（KPFM）检查了这些变化，结果表明，Ta掺杂后TiO ₂的费米能级向下移动，为电子从钙钛矿LUMO到TiO _2的转移提供了驱动力。导带导致更高的电流密度。此外，器件的阻抗谱分析表明，由于掺杂的薄膜具有更高的复合电阻，因此通过Ta掺杂可以降低电荷转移电阻，并可以提高R _sh。与未掺杂的TiO ₂相比，Ta掺杂为3.0％的PSC器件的总体效率提高了40％，其中最佳器件显示的功率转换效率约为。9.94％。