Understanding the Degradation of Methylenediammonium and Its Role in Phase-Stabilizing Formamidinium Lead Triiodide.
Understanding the Degradation of Methylenediammonium and Its Role in Phase-Stabilizing Formamidinium Lead Triiodide.
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DOI：
10.1021/jacs.3c01531
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发表时间：
2023-05-10
影响因子：
15
通讯作者：
Snaith, Henry J.
中科院分区：
文献类型：
--
作者：
Duijnstee, Elisabeth A.;Gallant, Benjamin M.;Holzhey, Philippe;Kubicki, Dominik J.;Collavini, Silvia;Sturdza, Bernd K.;Sansom, Harry C.;Smith, Joel;Gutmann, Matthias J.;Saha, Santanu;Gedda, Murali;Nugraha, Mohamad I.;Kober-Czerny, Manuel;Xia, Chelsea;Wright, Adam D.;Lin, Yen-Hung;Ramadan, Alexandra J.;Matzen, Andrew;Hung, Esther Y. -H.;Seo, Seongrok;Zhou, Suer;Lim, Jongchul;Anthopoulos, Thomas D.;Filip, Marina R.;Johnston, Michael B.;Nicholas, Robin J.;Delgado, Juan Luis;Snaith, Henry J.
三碘化甲脒铅（FAPbI3）是单结金属卤化物钙钛矿光伏电池的主要候选材料，尽管该相具有亚稳性。为了提高其环境相稳定性并创造世界纪录的光伏效率，二氯化亚二铵（MDACl2）被用作FAPbI3的添加剂。据报道，MDA2+与Cl -一起被并入钙钛矿晶格中。然而，MDA2+的确切功能和作用仍不确定。在这里，我们从含有MDACl2 （FAPbI3- m）的溶液中生长FAPbI3单晶。我们证明了FAPbI3-M晶体在环境条件下可以稳定地转变为光失活性δ相超过一年。重要的是，我们发现MDA2+不是材料稳定性增强的直接原因。相反，MDA2+迅速降解产生铵和甲胺，随后寡聚产生六亚甲基四胺（HMTA）。在含有HMTA （FAPbI3- h）的溶液中生长的FAPbI3晶体复制了FAPbI3- m增强的α-相稳定性。然而，我们进一步确定HMTA在钙钛矿前驱体溶液中是不稳定的，在钙钛矿前驱体溶液中可能与FA+发生反应，导致形成四氢三嗪（THTZ-H+）。通过液相和固态核磁共振技术的结合，我们发现THTZ-H+被选择性地掺入FAPbI3-M和FAPbI3-H的主体中，掺入量为~ 0.5 mol %，并推断这种掺入是α-相稳定性提高的原因。
Formamidinium lead triiodide (FAPbI3) is the leading candidate for single-junction metal–halide perovskite photovoltaics, despite the metastability of this phase. To enhance its ambient-phase stability and produce world-record photovoltaic efficiencies, methylenediammonium dichloride (MDACl2) has been used as an additive in FAPbI3. MDA2+ has been reported as incorporated into the perovskite lattice alongside Cl–. However, the precise function and role of MDA2+ remain uncertain. Here, we grow FAPbI3 single crystals from a solution containing MDACl2 (FAPbI3-M). We demonstrate that FAPbI3-M crystals are stable against transformation to the photoinactive δ-phase for more than one year under ambient conditions. Critically, we reveal that MDA2+ is not the direct cause of the enhanced material stability. Instead, MDA2+ degrades rapidly to produce ammonium and methaniminium, which subsequently oligomerizes to yield hexamethylenetetramine (HMTA). FAPbI3 crystals grown from a solution containing HMTA (FAPbI3-H) replicate the enhanced α-phase stability of FAPbI3-M. However, we further determine that HMTA is unstable in the perovskite precursor solution, where reaction with FA+ is possible, leading instead to the formation of tetrahydrotriazinium (THTZ-H+). By a combination of liquid- and solid-state NMR techniques, we show that THTZ-H+ is selectively incorporated into the bulk of both FAPbI3-M and FAPbI3-H at ∼0.5 mol % and infer that this addition is responsible for the improved α-phase stability.
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影响因子：
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