School of Advanced Materials and Nanotechnology, Xidian University, 266 Xinglong Section of Xifeng Road, Xi'an 710126, Shaanxi, People's Republic of China.
School of Advanced Materials and Nanotechnology, Xidian University, 266 Xinglong Section of Xifeng Road, Xi'an 710126, Shaanxi, People's Republic of China; State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, Xidian University, Xi'an 710071, Shaanxi, People's Republic of China.
J Colloid Interface Sci. 2023 Sep 15;646:517-528. doi: 10.1016/j.jcis.2023.05.058. Epub 2023 May 16.
Recently, two-dimensional (2D) transition metal carbides/nitrides (MXenes) find applications in perovskite solar cells (PSCs), due to their high conductivity, tunable electronic structures, and rich surface chemistry, etc. However, the integration of 2D MXenes into PSCs is limited by their large lateral sizes and relatively-small surface volume ratios, and the roles of MXenes in PSCs are still ambiguous. In this paper, zero-dimensional (0D) MXene quantum dots (MQDs) with an average size of 2.7 nm are obtained through clipping step by step combining a chemical etching and a hydrothermal reaction, which display rich terminals (i.e., -F, -OH, -O) and unique optical properties. The 0D MQDs incorporated into SnO electron transport layers (ETLs) of PSCs exhibit multifunction: 1) increasing the electrical conductivity of SnO, 2) promoting better alignments of energy band positions at the perovskite/ETL interface, 3) improving the film quality of atop polycrystalline perovskite. Particularly, the MQDs not only tightly bond with the Sn atom for decreasing the defects of SnO, but also interact with the Pb of perovskite. As a result, the defect density of PSCs is significantly decreased from 5.21 × 10 to 6.4 × 10 cm, leading to enhanced charge transport and reduced nonradiative recombination. Furthermore, the power conversion efficiency (PCE) of PSCs is substantially improved from 17.44% to 21.63% using the MQDs-SnO hybrid ETL compared with the SnO ETL. Besides, the stability of the MQDs-SnO-based PSC is greatly enhanced, with only ～4% degradation of the initial PCE after storage in ambient condition (25 °C, RH: 30-40%) for 1128 h, as compared to that of the reference device with a rapid degradation of ～60% of initial PCE after 460 h. And MQDs-SnO-based PSC also presents higher thermal stability than SnO-based device with continuous heating for 248 h at 85 °C. The unique MQDs exhibited in this work might also find other exciting applications such as light-emitting diodes, photodetectors, and fluorescent probes.
最近，二维（2D）过渡金属碳化物/氮化物（MXenes）由于其高导电性、可调谐的电子结构和丰富的表面化学等特点，在钙钛矿太阳能电池（PSCs）中得到了应用。然而，2D MXenes 集成到 PSCs 中受到其较大的横向尺寸和相对较小的表面积体积比的限制，并且 MXenes 在 PSCs 中的作用仍然不清楚。在本文中，通过逐步化学刻蚀和水热反应相结合的方法，得到了平均尺寸为 2.7nm 的零维（0D）MXene 量子点（MQDs），其具有丰富的末端（即-F、-OH、-O）和独特的光学性质。0D MQDs 掺入 PSCs 的 SnO 电子传输层（ETL）中，表现出多种功能：1）提高 SnO 的电导率，2）促进钙钛矿/ETL 界面能带位置更好地对齐，3）改善顶部多晶钙钛矿的薄膜质量。特别地，MQDs 不仅与 Sn 原子紧密结合以减少 SnO 的缺陷，而且还与钙钛矿的 Pb 相互作用。结果，PSC 的缺陷密度从 5.21×10 显著降低到 6.4×10 cm，导致电荷输运增强，非辐射复合减少。此外，与仅使用 SnO ETL 的 PSCs 相比，使用 MQDs-SnO 混合 ETL 的 PSCs 的功率转换效率（PCE）从 17.44%显著提高到 21.63%。此外，基于 MQDs-SnO 的 PSC 的稳定性得到了极大的提高，在环境条件（25°C，RH：30-40%）下储存 1128 小时后，初始 PCE 的降解仅约为 4%，而参考器件的初始 PCE 则迅速降解约 60%，在 460 小时后。并且与基于 SnO 的器件相比，基于 MQDs-SnO 的器件在 85°C 下连续加热 248 小时后具有更高的热稳定性。本工作中表现出的独特的 MQDs 可能还会在发光二极管、光电探测器和荧光探针等其他领域找到令人兴奋的应用。
