Benzodithiophene‐Based Spacers for Layered and Quasi‐Layered Lead Halide Perovskite Solar Cells

Abstract

Incorporating extended pi-conjugated organic cations in layered lead halide perovskites is a recent trend promising to merge the fields of organic semiconductors and lead halide perovskites. Herein, we integrate benzodithiophene (BDT) into Ruddlesden-Popper (RP) layered and quasi-layered lead iodide thin films (with methylammonium, MA) of the form (BDT) 2 MA nÀ 1 Pb n I 3n + 1 . The importance of tuning the ligand chemical structure is shown as an alkyl chain length of at least six carbon atoms is required to form a photoactive RP (n = 1) phase. With N = 20 or 100, as prepared in the precursor solution following the formula (BDT) 2 MA NÀ 1 Pb N I 3N + 1 , the performance and stability of devices surpassed those with phenylethylammonium (PEA). For N = 100, the BDT cation gave a power conversion efficiency of up to 14.7 % vs. 13.7 % with PEA. Transient photocurrent, UV photoelectron spectroscopy, and Fourier transform infrared spectroscopy point to improved charge transport in the device active layer and additional electronic states close to the valence band, suggesting the formation of a Lewis adduct between the BDT and surface iodide vacancies.

Effective Passivation of Perovskite Solar Cells Involving a Unique Secondary Ammonium Halide Modulator

“…First, the amount of two passivators was relatively small, which may be below the limit of detection. Second, the steric hindrance of benzothiophene increased the formation energy of corresponding LD perovskite, [32][33][34] while no additional energy was introduced since no annealing process involved. Thus, LD perovskite could hardly be formed.…”

Multifunctional π‐Conjugated Additives for Halide Perovskite

“…Reproduced with permission. [146] Copyright 2021, Wiley-VCH. drophobic, rigid, and bulky conjugated cations act as encapsulating layers to suppress ion migration, enhance moisture and environment stability while maintaining high conductivity compared to aliphatic cations.…”

“…in their recent works found the role of the linker length is critical for incorporation into 2D perovskite by preparing benzodithiophene (BDT)‐based cations with different alkane linkers (Figure 10d). [ 146 ] The BDT‐C2‐based perovskite film shows an extended absorption shoulder until ≈700 nm, which is quite similar to the films of pure BDT and evidence of extending self‐aggregation (Figure 10e). The shoulder absorption is absent in BDT‐C4 and BDT‐C6 based films.…”

“…e) Corresponding UV/Vis absorption and PL spectra. Reproduced with permission [146]. Copyright 2021, Wiley-VCH.…”

Fluorinated spacers: an effective strategy to tailor the optoelectronic properties and stability of metal-halide perovskites for photovoltaic applications

“…2,67 To date, versatile architectures of spacers, including aliphatic, aromatic or different heterocyclic scaffolds with varying anchoring groups, have been explored for RP- and DJ-type perovskites towards PV applications. 68–70 Examples of these different spacers are phenylethylammonium (PEA), 71 1,4-phenylenedimethylammonium, 72 benzylammonium (BA), 73 naphthalenemethylammonium, 74 anthracenemethylammonium, 74 4-(aminoethyl)pyridine, 75 alkylammoniumbenzodithiophene, 76 thiophene-2-ethylamine, 77 3- or 4-(aminomethyl)piperidinium, 78 benzamidine, 59 etc.…”