Methylammonium lead bromide (MAPbBr3) perovskite quantum dots (PQDs) passivated with capping ligands with different chain length, including butylamine-valeric acid (BUTY-VA), octylamine-caprylic acid (OCTY-CA), and dodecylamine-lauric acid (DODE-LA), are investigated to determine an optimized capping layer thickness for maximizing both electronic and antimoisture properties of perovskite materials in optoelectronic devices. The photoluminescence quantum yield (PLQY) is observed to be chain length dependent, where the PLQY of BUTY-VA, OCTY-CA, and DODE-LA MAPbBr3 PQDs is 82% ± 4%, 68% ± 7%, and 18% ± 2%, respectively. Electrochemical impedance spectroscopy (EIS) measurements of each PQD film reveal that there is a slight increase in conductivity from reducing the capping ligand chain length from 8 carbon atoms (OCTY-CA) to 4 carbon atoms (BUTY-VA). Using the Butler-Volmer equation, the charge transfer factor β for BUTY-VA and OCTY-CA MAPbBr3 PQD films in a tetrabutylammonium hexafluorophosphate-dichloromethane electrolyte solution was calculated to be 0.36 and 0.31, respectively. From an Arrhenius analysis, the activation energy (Ea) for charge transport between the PQD film and the electrolyte was calculated to be 77 and 90 meV for BUTY-VA and OCTY-CA MAPbBr3 PQD films, respectively. Moreover, passivating PQDs with capping ligands with 12 carbon atoms (DODE-LA) almost completely insulates the PQDs and diminishes charge transport. This is also observed in transient photocurrent density measurements. The results suggest that the inter-PQD distance in this solid film is too long for effective tunneling to occur. However, using BUTY-VA capping ligands to improve electronic properties of PQD solid film comes with a cost of stability.

中文翻译：

---

钙钛矿量子点的稳定性以及电子和光学性质对封端配体链长的依赖性。

甲基铵溴化铅（MAPbBr3）钙钛矿量子点（PQD）被具有不同链长的封端配体钝化，包括丁胺-戊酸（BUTY-VA），辛基胺-辛酸（OCTY-CA）和十二烷基胺-月桂酸（DODE- LA）被研究以确定最佳的覆盖层厚度，以最大化光电器件中钙钛矿材料的电子和防潮性能。观察到光致发光量子产率（PLQY）与链长有关，其中BUTY-VA，OCTY-CA和DODE-LA MAPbBr3 PQD的PLQY为82％±4％，68％±7％和18％±分别为2％。每个PQD膜的电化学阻抗谱（EIS）测量表明，将封端配体链长从8个碳原子（OCTY-CA）减少到4个碳原子（BUTY-VA），导电率略有增加。使用Butler-Volmer方程，六氟磷酸四丁铵-二氯甲烷电解质溶液中的BUTY-VA和OCTY-CA MAPbBr3 PQD薄膜的电荷转移因子β分别计算为0.36和0.31。根据Arrhenius分析，对于BUTY-VA和OCTY-CA MAPbBr3 PQD膜，在PQD膜和电解质之间进行电荷传输的活化能（Ea）分别为77和90 meV。此外，用具有12个碳原子的封端配体钝化的PQD（DODE-LA）几乎完全隔离了PQD，并减少了电荷传输。在瞬态光电流密度测量中也观察到了这一点。结果表明，该固体膜中的PQD间距离太长，无法进行有效的隧穿。然而，