Enhancing Charge Transport of 2D Perovskite Passivation Agent for Wide‐Bandgap Perovskite Solar Cells Beyond 21%

Abstract

The replacement of a small amount of organic cations with bulkier organic spacer cations in the perovskite precursor solution to form a 2D perovskite passivation agent (2D‐PPA) in 3D perovskite thin films has recently become a promising strategy for developing perovskite solar cells (PSCs) with long‐term stability and high efficiency. However, the long, bulky organic cations often form a barrier, hindering charge transport. Herein, for the first time, 2D‐PPA engineering based on wide‐bandgap (≈1.68 eV) perovskites are reported. Pentafluorophenethylammonium (F5PEA+) is introduced to partially replace phenylethylammonium (PEA+) as the 2D‐PPA, forming a strong noncovalent interaction between the two bulky cations. The charge transport across and within the planes of pure 2D perovskites, based on mixed ammoniums, increases by a factor of five and three compared with that of mono‐cation 2D perovskites, respectively. The perovskite films based on mixed‐ammonium (F5PEA+‐PEA+) 2D‐PPA exhibit similar surface morphology and crystal structure, but longer carrier lifetime, lower exciton binding energy, less trap density and higher conductivity, in comparison with those using mono‐cation (PEA+) 2D‐PPA. The performance of PSCs based on mixed‐cation 2D‐PPA is enhanced from 19.58% to 21.10% along with improved stability, which is the highest performance for reported wide‐bandgap PSCs.

All-Perovskite Tandem Solar Cells: A Roadmap to Uniting High Efficiency with High Stability

“…46 By further tailoring the spacers in 2D−3D heterostructures to improve charge transport, WBG PSCs with PCEs over 21% have been achieved. 47 Chen et al revealed that more conductive and defective grain boundaries of WBG films fundamentally limit the V OC of WBG PSCs, and the bulky organic ammonium additives created an ion diffusion barrier and reduced the accumulation of detrimental ionic defects at grain boundaries. 48 Doherty et al observed the compositional inhomogeneity of Br−I mixedhalide perovskite grains with more trap clusters appearing at the interfaces between inhomogeneous grains and homogeneous surrounding material.…”

Emerging doping strategies in two-dimensional hybrid perovskite semiconductors for cutting edge optoelectronics applications

“…9(d)). 116 Br doping in the 2D PEAI derived perovskite capping layer also passivated the interfacial defects resulting in a decrease in interfacial charge recombination and increase in carrier lifetime which could improve the overall PCE of 2D capped 3D perovskite solar cells with improved stability. 117 The uorinated organic spacer was reported to enhance the efficiency of the device due to enhancement in the dipole moment and the dielectric constant of the organic molecules, which facilitated efficient charge separation.…”

Multiple‐Ring Aromatic Spacer Cation Tailored Interlayer Interaction for Efficient and Air‐Stable Ruddlesden–Popper Perovskite Solar Cells

“…[19] The interaction is determined by an entanglement of large ammonium bilayers characterized by intermolecular force. [20] Ren et al reported a new type of organic spacer cation containing S atoms, 2-(methylthio)ethylamine hydrochloride (MTEACl). The formed (MTEA) 2 MA 4 Pb 5 I 16 perovskite with strong out-of-plane preferential growth induced by the S-S interaction enables efficient charge transport and device stability.…”