Consolidating a Pb–X framework via multifunctional passivation with fluorinated zwitterions for efficient and stable perovskite solar cells

Abstract

Multifunctional fluorinated D-PFPAA zwitterions can reduce the number of ionic defects and consolidate Pb–X framework, suppressing ion migration, and form a hydrophobic barrier, significantly improving the power conversion efficiency and stability.

Potassium Salt Coordination Induced Ion Migration Inhibition and Defect Passivation for High-Efficiency Perovskite Solar Cells

“…40,41 Furthermore, ultraviolet−visible (UV− vis) spectrophotometry indicates that OAPS slightly enhances the absorption of perovskite films in the wavelength range of 320−480 nm (Figure S2), probably due to the increased light scattering of PbI 2 . 13,42 For demonstrating the mechanism of OAPS to perovskite, X-ray photoelectron spectroscopy (XPS) and Fourier transfer infrared spectroscopy (FTIR) of perovskite and OAPS are characterized. The XPS full spectra are shown in Figure S3.…”

“…Because of the excellent photovoltaic properties such as long carrier diffusion length, high carrier mobility, low exciton binding energy, and high absorbance, perovskites have been widely studied as the light absorption material of solar cells. − In the past decade, the certified power conversion efficiency (PCE) of perovskite solar cells (PSCs) has been promoted from 3.8 to 25.7% . However, the disordered trap states distributed in the perovskites seriously impair the PCE of PSCs, whereas the cation and anion defects such as uncoordinated Pb 2+ , uncoordinated I – , and a Pb–I antisite capture charge carriers. − Trap states at grain boundaries not only act as the carrier recombination center, inducing nonradiative recombination and contributing to the major loss mechanism, but also result in the rapid decomposition of a polycrystalline perovskite as the channels for the diffusion of moisture and oxygen, causing the PCE degradation. − In addition, due to the iodide Frenkel defect caused by ion migration of I – , PSCs cannot reach the maximum power output immediately under illumination, known as the hysteresis of PSCs …”

“…According to Bragg’s law, plane distance is inversely proportional to the diffraction angle. The shift of diffraction peaks indicates the increase of perovskite plane distance, and this lattice expansion can be attributed to the interstitial occupation of K + , which could increase the ion migration barrier. , Furthermore, ultraviolet–visible (UV–vis) spectrophotometry indicates that OAPS slightly enhances the absorption of perovskite films in the wavelength range of 320–480 nm (Figure S2), probably due to the increased light scattering of PbI 2 . , …”

Full Life-Cycle Lead Management and Recycling Transparent Conductors for Low-Cost Perovskite Solar Cell

“…Despite their promise, there still exist the toxicity issues associated with the Pb content of high-performing PSCs during a photovoltaic device’s lifetime . A direct strategy to avoid a potential threat to the environment is to completely replace the Pb counterpart in the perovskite crystal structure, but all currently used lead-free perovskites like tin-containing perovskite are facing intractable problems such as poor stability and low PCE. − Apart from the replacement of lead, in recent years, some explorations to immobilize Pb and prevent them escaping from perovskite into the environment have been performed, through either polymer protection network building, metal-framework capture, or ion migration inhibition. − Particularly, inhibiting Pb ion migration by one-step introduction of an additive into a precursor to form a robust perovskite is a relatively facile and green method, compared to the in situ polymerization process of a gradient-annealing-dependent polymer network and multistep synthesis process of a heavy-metal-containing metal framework. , Various additives have been explored to inhibit Pb ion migration in perovskite . Of these, green pseudo halide (pseudo-X) ions with a cheap market price (e.g., HCOO – and Ac – ) as additives have been demonstrated to be effective in inhibiting Pb ion migration via the strong interaction with undercoordinated Pb in perovskite, in keeping with a high PCE. − …”

“…10−13 Particularly, inhibiting Pb ion migration by one-step introduction of an additive into a precursor to form a robust perovskite is a relatively facile and green method, compared to the in situ polymerization process of a gradient-annealing-dependent polymer network and multistep synthesis process of a heavy-metal-containing metal framework. 14,15 Various additives have been explored to inhibit Pb ion migration in perovskite. 16 Of these, green pseudo halide (pseudo-X) ions with a cheap market price (e.g., HCOO − and Ac − ) as additives have been demonstrated to be effective in inhibiting Pb ion migration via the strong interaction with undercoordinated Pb in perovskite, in keeping with a high PCE.…”