Ciccioli Andrea, Latini Alessandro
Department of Chemistry , Sapienza - University of Rome , Piazzale Aldo Moro 5 , 00185 Rome , Italy.
J Phys Chem Lett. 2018 Jul 5;9(13):3756-3765. doi: 10.1021/acs.jpclett.8b00463. Epub 2018 Jun 27.
The role of thermodynamics in assessing the intrinsic instability of the CHNHPbX perovskites (X = Cl,Br,I) is outlined on the basis of the available experimental information. Possible decomposition/degradation pathways driven by the inherent instability of the material are considered. The decomposition to precursors CHNHX(s) and PbX( s) is first analyzed, pointing out the importance of both the enthalpic and the entropic factor, the latter playing a stabilizing role making the stability higher than often asserted. For CHNHPbI, the disagreement between the available calorimetric results makes the stability prediction uncertain. Subsequently, the gas-releasing decomposition paths are discussed, with emphasis on the discrepant results presently available, probably reflecting the predominance of thermodynamic or kinetic control. The competition between the formation of NH(g) + CHX(g), CHNH(g) + HX(g) or CHNHX(g) is analyzed, in comparison with the thermal decomposition of methylammonium halides. In view of the scarce and inconclusive thermodynamic studies to-date available, the need for further experimental data is emphasized.
基于现有的实验信息，概述了热力学在评估CHNHPbX钙钛矿（X = Cl、Br、I）固有不稳定性方面的作用。考虑了由材料固有不稳定性驱动的可能的分解/降解途径。首先分析了向前驱体CHNHX(s)和PbX(s)的分解，指出了焓因素和熵因素的重要性，后者起到稳定作用，使稳定性高于通常所宣称的。对于CHNHPbI，现有的量热结果之间的分歧使得稳定性预测具有不确定性。随后，讨论了气体释放分解途径，重点关注目前可用的不一致结果，这可能反映了热力学或动力学控制的主导地位。与卤化甲铵的热分解相比，分析了NH(g) + CHX(g)、CHNH(g) + HX(g)或CHNHX(g)形成之间的竞争。鉴于目前可用的热力学研究稀缺且尚无定论，强调了进一步实验数据的必要性。
