Halogen Engineering for Operationally Stable Perovskite Solar Cells via Sequential Deposition

Abstract

The performance of perovskite solar cells (PSCs) relies on the synthesis method and chemical composition of the perovskite materials. So far, PSCs that have adopted two‐step sequential deposited perovskite with the state‐of‐art composition (FAPbI3)1−x(MAPbBr3)x (x < 0.05) have achieved record power conversion efficiency (PCE), while their one‐step antisolvent dripping counterparts with typical composition Cs0.05FA0.81MA0.14Pb(I0.85Br0.15)3 with more bromine have exhibited much better long‐term operational stability. Thus, halogen engineering that aims to elevate bromine content in sequential deposited perovskite film would push operational stability of PSCs toward that of antisolvent dripping deposited perovskite materials. Here, a Br‐rich seeding growth method is devised and perovskite seed solution with high bromine content is introduced into a PbI2 precursor, leading to bromine incorporation in the resulting perovskite film. Photovoltaic devices fabricated by Br‐rich seeding growth method exhibit a PCE of 21.5%, similar to 21.6% for PSCs having lower bromine content. Whereas, the operational stability of PSCs with higher bromine content is significantly enhanced, with over 80% of initial PCE retained after 500 h tracking at maximum power point under 1‐sun illumination. This work highlights the vital importance of halogen composition for the operational stability of PSCs, and introduces an effective way to incorporate bromine into mixed‐cation‐halide perovskite film via sequential deposition method.

Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

“…The intrinsic degradation mechanisms concern pristine perovskite materials subjected to temperature [3] and illumination [4], while extrinsic degradation mechanisms are determined by foreign species and molecules such as oxygen [5,6] and water [7]. These are typically addressed by chemical engineering, most notably, using mixtures of cations [8] and halogens [9], doping and passivation [10]. The multitude of new organic cations renders a wide variety of low-dimensional perovskite structures, where ion migration is inhibited by the relatively large cations and their embedded hydrophobic moieties can reduce the detrimental effect of water molecules.…”

Mechanisms and Suppression of Photoinduced Degradation in Perovskite Solar Cells

“…[ 134–137 ] Besides, the halide content management is also a key to improving the perovskite phase stability. [ 69,138 ]…”

“…[134][135][136][137] Besides, the halide content management is also a key to improving the perovskite phase stability. [69,138] Layered structure (2D/3D mixed perovskites) has proven to be a new way to suppress the ion migration. Xiao et al observed suppressed ion migration along the in-plane direction of layered perovskites at varied temperatures, as the formation energy of ion vacancy in 2D structure is higher than that in 3D perovskites.…”

Lead and Iodide Fixation by Thiol Copper(II) Porphyrin for Stable and Environmental-Friendly Perovskite Solar Cells

“…23 Introducing other halide anions (such as F − , Cl − , or Br − ) into perovskite film increased the lattice strain relaxation of perovskite, to improve the long-term durability of PSCs. [24][25][26] In our recent work, the ammonium/amine porphyrin or phthalocyanine macromolecules with excellent photoelectric properties was used to treat the perovskite film to obtain efficient surface and GBs modification and interfacial charge transfer, thus significantly enhancing the performance and stability of PSCs. 3,12,27 Since the defects mainly locate at the top surface of the perovskite film, 10,28 it is still a challenge to effectively encapsulate and modulate the perovskite surface to fabricate the efficient, stable, and environmental-friendly PSCs.…”