Synergistic Surface Passivation of CH3 NH3 PbBr3 Perovskite Quantum Dots with Phosphonic Acid and (3-Aminopropyl)triethoxysilane

Ke Xu; Evan T Vickers; Longshi Rao; Sarah A Lindley; A'Lester C Allen; Binbin Luo; Xueming Li; Jin Zhong Zhang

doi:10.1002/chem.201805656

Synergistic Surface Passivation of CH₃ NH₃ PbBr₃ Perovskite Quantum Dots with Phosphonic Acid and (3-Aminopropyl)triethoxysilane

Chemistry. 2019 Apr 1;25(19):5014-5021. doi: 10.1002/chem.201805656. Epub 2019 Mar 6.

Authors

Ke Xu^{1

2}, Evan T Vickers¹, Longshi Rao³, Sarah A Lindley¹, A'Lester C Allen¹, Binbin Luo⁴, Xueming Li², Jin Zhong Zhang¹

Affiliations

¹ Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA, 95064, USA.
² College of Chemistry and Chemical Engineering, Chongqing University, Chongqing, 400030, P.R. China.
³ School of Mechanical and Automotive Engineering, South China University of Technology, Guangdong, 510640, P.R. China.
⁴ Department of Chemistry, Shantou University, Guangdong, 515063, P.R. China.

PMID: 30682220
DOI: 10.1002/chem.201805656

Abstract

CH₃ NH₃ PbBr₃ perovskite quantum dots (PQDs) are synthesized by using four different linear alkyl phosphonic acids (PAs) in conjunction with (3-aminopropyl)triethoxysilane (APTES) as capping ligands. The resultant PQDs are characterized by means of XRD, TEM, Raman spectroscopy, FTIR spectroscopy, UV/Vis, photoluminescence (PL), time-resolved PL, and X-ray photoelectron spectroscopy (XPS). PA chain length is shown to control the PQD size (ca. 2.9-4.2 nm) and excitonic absorption band positions (λ=488-525 nm), with shorter chain lengths corresponding to smaller sizes and bluer absorptions. All samples show a high PL quantum yield (ca. 46-83 %) and high PL stability; this is indicative of a low density of band gap trap states and effective surface passivation. Stability is higher for smaller PQDs; this is attributed to better passivation due to better solubility and less steric hindrance of the shorter PA ligands. Based on the FTIR, Raman, and XPS results, it is proposed that Pb²⁺ and CH₃ NH₃ ⁺ surface defects are passivated by R-PO₃ ^2- or R-PO₂ (OH)^- , whereas Br^- surface defects are passivated by R-NH₃ ⁺ moieties. This study establishes the combination of PA and APTES ligands as a highly effective dual passivation system for the synergistic passivation of multiple surface defects of PQDs through primarily ionic bonding.

Keywords: ligand effects; perovskite phases; quantum dots; surface analysis; synthesis design.

Abstract

Grants and funding