fig2

From: Electron-donor/-acceptor ratio-guided molecular engineering for buried interface optimization in n-i-p perovskite solar cells

Figure 2. Interactions between dipolar molecules and SnO₂/perovskite films. (A) N 1s, (B) Sn 3d, (C) O 1s XPS spectra, and (D) FTIR spectra of control, AA-, ABA-, and DBA-modified SnO₂ films. XPS spectra of (E) N 1s, (F) Pb 4f, and (G) I 3d for control, AA-, ABA-, and DBA-modified perovskite films; (H) Schematic comparison of interaction strengths of AA, ABA, and DBA with SnO₂ and perovskite films; (I) Coordination geometry and adsorption energy of -COO^- from AA, ABA, and DBA on SnO₂ films; (J) Coordination geometry and adsorption energy of -NH₃⁺ from AA, ABA, and DBA on perovskite films. XPS: X-ray photoelectron spectroscopy; FTIR: Fourier transform infrared; AA: L-aspartic acid; ABA: 4-aminobutyric acid; DBA: L-2,4-diaminobutyric acid.