Dimensionality and Defect Engineering Using Fluoroaromatic Cations for Efficiency and Stability Enhancement in 3D/2D Perovskite Photovoltaics

Abstract

State‐of‐the‐art perovskite solar cells (PSCs) based on three‐dimensional (3D) films have achieved high power conversion efficiencies (PCEs), but are relatively fragile in high‐temperature and humid environments. This shortcoming must be addressed before PSCs can be fully commercialized. Herein, the use of a fluorinated aromatic organic spacer cation, 4‐fluoro‐phenethylammonium iodide (FPEAI), to fine‐tune the dimensionality and surface morphology of perovskite films is demonstrated. Surface treatment with FPEAI can lead to in situ formation of a two‐dimensional (2D) (FPEA)2PbI4 perovskite capping layer atop a 3D perovskite film, producing novel 3D/2D interface in perovskite films. Simultaneously, FPEAI treatment can induce a novel grain‐boundary passivation effect on the film surface, which helps to suppress undesirable charge recombination. After FPEAI treatment, standard (0.09 cm2) and large‐area (2.00 cm2) PSCs achieve PCEs of 20.53% and 16.82%, respectively. The FPEAI‐treated PSCs also demonstrate superior air‐ and photo‐stability due to the hydrophobic (FPEA)2PbI4 capping layer that reduces moisture ingress into perovskite structures. Furthermore, a 11.2 cm2 large FPEAI‐treated PSC module with a PCE of 13.66% are successfully fabricated. FPEAI passivation is a facile strategy to produce 3D/2D multi‐dimensional PSCs with superior performance and stability.

Stability of Perovskite Solar Cells: Degradation Mechanisms and Remedies

“…Fluoroarene-based RP 2D perovskite can highly stabilize the device owing to the ultra-hydrophobicity of pentafluorophenylethylammonium spacer cation (Liu et al, 2019). Large area PSC module could be fabricated with excellent ambient-and photo-stability when 4-fluorophenethylammonium iodide has been employed (Lee et al, 2021). Aromatic formamidiniums are proven to be effective spacer due to its ability to make multiple NH.…”

Water-Assisted Perovskite Quantum Dots with High Optical Properties

“…The PL decay curve indicated that the PL lifetime of the MAPbBr 3 PeQDs increased to 15.4 ns with 5 µL of assisted water compared to 12.6 ns without water. From these results, the longer τ ave of the prepared MAPbBr 3 PeQDs with assisted water of 5 µL indicates that the surface defects on the large MAPbBr 3 PeQDs were passivated by small MAPbBr 3 PeQDs as an Ostwald ripening, resulting in efficiently suppressing non-radioactive recombination by small PeQD passivation on their surface [29,30]. On the other hand, in the prepared MAPbBr 3 PeQDs with assisted water over 5 µL, the excess water worked to collapse MAPbBr 3 PeQDs because of their polarity, and it caused the increasing of MAPbBr 3 PeQD surface defects, resulting in a shorter τ ave .…”

Room‐Temperature Spray Deposition of Large‐Area SnO2 Electron Transport Layer for High Performance, Stable FAPbI3‐Based Perovskite Solar Cells

“…A blue laser source of 473 nm (CNI laser, MBL‐FN‐473) was used as a perturbation source, along with a white LED for background illumination. [ 43,52 ] A time‐resolved PL (TRPL) study was performed using an inverted‐type scanning confocal microscope (MicroTime‐200, Picoquant, Germany) with a 4 × (air) objective. The lifetime measurements were performed using a single‐mode pulsed diode laser (470 nm with a pulse width of ≈30 ps and an average power of ≈100 nW in 200 kHz repetition rate) as an excitation source.…”