Enhancing Photostability of Complex Lead Halides through Modification with Antibacterial Drug Octenidine

Abstract

The high power-conversion efficiencies of hybrid perovskite solar cells encourage many researchers. However, their limited photostability represents a serious obstacle to the commercialization of this promising technology. Herein, we present an efficient method for improving the intrinsic photostability of a series of commonly used perovskite material formulations such as MAPbI₃, FAPbI₃, Cs_0.12FA_0.88PbI₃, and Cs_0.10MA_0.15FA_0.75PbI₃ through modification with octenidine dihydroiodide (OctI₂), which is a widely used antibacterial drug with two substituted pyridyl groups and two cationic centers in its molecular framework. The most impressive stabilizing effects were observed in the case of FAPbI₃ and Cs_0.12FA_0.88PbI₃ absorbers that were manifested in significant suppression or even blocking of the undesirable perovskite films' recrystallization and other decomposition pathways upon continuous 110 mW/cm² light exposure. The achieved material photostability-within 9000 h for the Oct(FA)_n-1Pb_nI_3n+1 (n = 40-400) and 20,000 h for Oct(Cs_0.12FA_0.88)_n-1Pb_nI_3n+1 (where n = 40-400) formulations-matches the highest values ever reported for complex lead halides. It is important to note that the stabilizing effect is maintained when OctI₂ is used only as a perovskite surface-modifying agent. Using a two-cation perovskite composition as an example, we showed that the performances of the solar cells based on the developed Oct(Cs_0.12FA_0.88)₃₉₉Pb₄₀₀I₁₂₀₁ absorber material are comparable to that of the reference devices based on the unmodified perovskite composition. These findings indicate a great potential of the proposed approach in the design of new highly photostable and efficient light absorbers. We believe that the results of this study will also help to establish important guidelines for the rational material design to improve the operational stability of perovskite solar cells.

Keywords: 2D/3D hybrid perovskites; complex lead halides; molecular additives; molecular modifiers; perovskite solar cells; photostability.

Figure 1

Molecular structure of octenidine dihydroiodide (a) and a schematic illustration of the Dion–Jacobson phase that could be formed as a result of OctI₂ integration into crystal lattice (b).

Figure 2

Evolution of the UV–Vis spectra of the Oct(A)_n−1Pb_nI_3n+1 films depending on the OctI₂ loading as compared to the reference APbI₃ samples, where A = MA (a,e,i), FA (b,f,j), Cs_0.12FA_0.88 (c,g,k), and Cs_0.1MA_0.15FA_0.75 (d,h,l) as a function of the aging time.

Figure 3

AFM topography (a) and s-SNOM amplitude images for the Oct(Cs_0.1MA_0.15FA_0.75)₃₉Pb₄₀I₁₂₁ film recorded at the characteristic frequency of OctI₂ (b). XPS survey, N 1s, Pb 4f_7/2 and I 3d_5/2 spectra of glass/MAPbI₃ (c) and glass/Oct(MA)₃₉Pb₄₀I₁₂₁ (d) films before (as prepared) and after exposure to light for 1464 h (aged).

Figure 4

XRD patterns of the Oct(A)_n−1Pb_nI_3n+1 films and the reference APbI₃ samples before and after light soaking for 1464 h (A = MA) (a,e,i), 9000 h (A = FA) (b,f,j), 20,000 h (A = Cs_0.12FA_0.88) (c,g,k), and 5000 h (A = Cs_0.1MA_0.15FA_0.75) (d,h,l).

Figure 5

Device architecture (a), current–voltage characteristics (b), and EQE spectra (b) of the champion devices based on the pristine and modified perovskite films Oct(Cs_0.12FA_0.88)_n−1Pb_nI_3n+1 with different OctI₂ contents (c). The power conversion efficiency (PCE) of the ITO/PTA/perovskite/PCBM/Al devices based on the pristine and modified Oct(Cs_0.12FA_0.88)_n−1Pb_nI_3n+1 perovskite films before and after exposure to light (70 mW/cm², T = 38 ± 3°C) for 170 h in inert atmosphere (d).