Uncovering the Mechanism of Poly(ionic‐liquid)s Multiple Inhibition of Ion Migration for Efficient and Stable Perovskite Solar Cells

Abstract

make it one of the most promising photovoltaic technologies. [1,2] Although such solar cells have been demonstrated with a certified power conversion efficiency (PCE) reaching 25.5% for laboratory scale devices, [3] successful commercialization of PVSCs still lacks mature large-area manufacturing technology and reliable long-term stability. [4] With the continuous improvement of printing technology, the fabrication of large-area perovskite photovoltaic devices has become possible and is expected to be compatible with industrial-level manufacturing in the coming future. [5,6] However, the intrinsic and extrinsic instabilities of PVSCs remain the tremendous hurdles on the road to commercialization.The photovoltaic performance of perovskite materials is vulnerable to operating environment. In general, the main degradation pathways of perovskite can be classified as two broad categories: one is susceptible to irreversible degradation under external environment stimulants (moisture, oxygen, heat, UV light, etc.) [7] and the other arises due to intrinsic defects caused by ion migration and organic cations or halide ions losses. [8] Generally speaking, aging degradation caused by hydration and oxidation (with assistance of external stress of moisture, oxygen, etc.) can be addressed with advanced encapsulation techniques. [9] However, numerous theoretical calculations and experimental observations document that the intrinsic ion migration phenomenon of hybrid perovskite materials cannot be avoided by encapsulation. [10,11] Thus far, almost all reported high-efficiency PVSCs are based on solution-prepared ionic polycrystalline perovskite absorbers, whose ionic characteristics make them prone to phase segregation, chemical degradation, and current-voltage hysteresis of devices, especially when suffering from illumination, heat, or external electric field. [12][13][14] Ironically, although the migratory ions can passivate the interface to promote carrier transport and collection in some special cases, it brings more serious hysteresis effects and stability issues in perovskite photovoltaic devices. [15,16] The problematics of the ion migration in perovskite can be ascribed to the lower activation energies (0.2-0.8 eV) of the organic and halide ions (e.g., MA + or I − ), which makes the ions

Mixed dimensionality of 2D/3D heterojunctions for improving charge transport and long-term stability in high-efficiency 1.63 eV bandgap perovskite solar cells

“…We can find that the migration distances are extended for both R-α-MBA- and R-α-BrMBA-incorporated cases. 67 Furthermore, the calculated migration energy for R-α-MBA- and R-α-BrMBA-incorporated cases are around two-fold higher than that of the control. 68 The substantially higher migration energy indicates that I − ion migration in the 2D/3D layers is suppressed significantly, which may be due to the steric impediment effect from larger spacer cations.…”

Recent Progress in Ionic Liquids for Stability Engineering of Perovskite Solar Cells

“…[71,77] Moreover, the functionalized ILs with imidazolium group or quaternary ammonium groups, which are enabled with the ability to form hydrogen bonds with the I À , Br À , and Cl À in perovskite materials, effective anchoring the I À , Br À , and Cl À for inhibition of instability caused by ion migration. [78] The formation of O⋯H-N hydrogen bonds between the carboxyl and ester groups in ILs with MA þ or FA þ also leads to the stabilization of organic ions. [79] The photovoltaic parameters of stable ILs-treated PSCs through chemical interaction are summarized in Table 3.…”

“…As a result, the PEa poly‐RTMS‐treated PSCs displayed a high PCE of 21.4% and a long‐term operational stability that remained more than 92% of its initial efficiency after 1200 h at 70−75 °C. Taking the advantage of formation of chemical interaction in the multiple repeating units, the PILs [poly‐1,3‐ bis (4‐ethylbenzyl)‐imidazolium chloride (PIL‐[bebim]Cl)], [ 54 ] [poly‐1‐vinyl benzyl‐triethylammonium chloride (PIL‐Am)], and [poly‐1‐vinyl benzyl‐3‐methylimidazole chloride (PIL‐Im)] [ 78 ] have been also employed to improve device stability. These PILs that combine the advantage of polymers and ILs include the structural designability, excellent chemical durability and thermal stability, which adds to the polymerizable ILs or PILs the potential of prolonging the service life of the device.…”

Interface Engineering with Quaternary Ammonium-Based Ionic Liquids toward Efficient Blue Perovskite Light-Emitting Diodes

“…27 In perovskite optoelectronic devices, ILs have been shown to passivate defects, 28 improve stability, 29 and replace traditional solvents to control crystal growth kinetics. 30 Although ILs have been widely employed to enhance the performance of perovskite solar cells (PSCs), 31 their application in PeLEDs is barely reported. 32,33 Here, we demonstrated that the use of quaternary ammonium salt-based ILs as the interfacial modification layer can greatly improve the efficiency and stability of the blue PeLEDs.…”