School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
Nanoscale. 2018 Jan 3;10(2):773-790. doi: 10.1039/c7nr06812c.
The current work reports the simultaneous enhancement in efficiency and stability of low-temperature, solution-processed triple cation based MAFARbPbI (MA: methyl ammonium, FA: formamidinium, Rb: rubidium) perovskite solar cells (PSCs) by means of adsorbed carbon nanomaterials at the perovskite/electron transporting layer interface. The quantity and quality of the adsorbents are precisely controlled to electronically modify the ETL surface and lower the energy barrier across the interface. Carbon derivatives namely fullerene (C) and PCBM ([6,6]-phenyl C71 butyric acid methyl ester) are employed as adsorbents in conjunction with ZnO and together serve as a bilayer electron transporting layer (ETL). The adsorbed fullerene (C-ZnO, abbreviated as C-ZnO) passivates the interstitial trap-sites of ZnO with interstitial intercalation of oxygen atoms in the ZnO lattice structure. C-ZnO ETL based PSCs demonstrate about a 19% higher average PCE compared to conventional ZnO ETL based devices and a nearly 9% higher average PCE than PCBM adsorbed-ZnO (P-ZnO) ETL based PSCs. In addition, the interstitial trap-state passivation with a C-ZnO film upshifts the Fermi-level position of the C-ZnO ETL by 130 meV, with reference to the ZnO ETL, which contributes to an enhanced n-type conductivity. The photocurrent hysteresis phenomenon in C-ZnO PSCs is also substantially reduced due to mitigated charge trapping phenomena and concomitant reduction in an electrode polarization process. Another major highlight of this work is that, C-ZnO PSCs demonstrate a superior device stability retaining about 94% of its initial PCE in the course of a month-long, systematic degradation study conducted in our work. The enhanced device stability with C-ZnO PSCs is attributed to their high resistance to aging-induced recombination phenomena and a water-induced perovskite degradation process, due to a lower content of oxygen-related chemisorbed species on the C-ZnO ETL. The intricate mechanisms behind the efficiency and stability enhancement are investigated in detail and explained in the context of enhanced surface and interfacial electronic properties.
本工作报道了通过在钙钛矿/电子传输层界面处吸附碳纳米材料，同时提高低温溶液处理的三阳离子基 MAFARbPbI（MA：甲基铵，FA：甲脒，Rb：铷）钙钛矿太阳能电池（PSC）的效率和稳定性。吸附剂的数量和质量得到精确控制，以对电子传输层表面进行电子修饰，并降低界面处的能量势垒。碳衍生物，即富勒烯（C）和 PCBM（[6,6]-苯基 C71 丁酸甲酯），与 ZnO 一起用作吸附剂，并共同作为双层电子传输层（ETL）。吸附的富勒烯（C-ZnO，简称 C-ZnO）通过氧原子在 ZnO 晶格结构中的间隙插入，钝化 ZnO 的间隙陷阱位。基于 C-ZnO 的 ETL 的 PSC 比基于传统 ZnO ETL 的器件平均 PCE 提高约 19%，比基于 PCBM 吸附 ZnO（P-ZnO）ETL 的 PSC 平均 PCE 提高近 9%。此外，与 ZnO ETL 相比，C-ZnO 薄膜中的间隙陷阱态钝化使 C-ZnO ETL 的费米能级位置向上移动 130 meV，这有助于提高 n 型导电性。由于电荷俘获现象得到缓解，以及电极极化过程的协同减少，C-ZnO PSC 中的光电流滞后现象也大大减少。这项工作的另一个主要亮点是，C-ZnO PSC 在我们的工作中进行的长达一个月的系统降解研究中，保留了初始 PCE 的约 94%，表现出优异的器件稳定性。C-ZnO PSC 的器件稳定性提高归因于其对老化诱导的复合现象和水诱导的钙钛矿降解过程具有较高的抵抗力，这是由于 C-ZnO ETL 上氧相关化学吸附物种的含量较低所致。详细研究了效率和稳定性提高的复杂机制，并结合增强的表面和界面电子特性进行了解释。
