Formamidinium (FA) based perovskites are considered as one of the most promising light-absorbing perovskite materials owing to their narrower band gap and better thermal stability compared to conventional methylammonium-based perovskites. Constant improvement by using various additives stimulates the potential application of these perovskites. Amine molecules with different structures have been widely used as typical additives in FA-based perovskite solar cells, and decent performances have been achieved. Thus, a systematic review focusing on structural regulation and functional construction of amines in FA-based perovskites is of significance. Herein, we analyze the construction mechanism of different structural amines on the functional perovskite crystals. The influence of amine molecules on specific perovskite properties including defect conditions, charge transfer, and moisture resistance are evaluated. Finally, we summarize the design rules of amine molecules for the application in high-performance FA-based perovskites and propose directions for the future development of additive molecules. 

From Structural Design to Functional Construction: Amine Molecules in High‐Performance Formamidinium‐Based Perovskite Solar Cells

Understanding steric-charge-dependence of conjugated passivators on π-Pb2+ bond strength for efficient all-inorganic perovskite solar cells

Organic-inorganic Pb-based halide perovskite photoelectrical materials, especially perovskite solar cells (PSCs), have attracted attention due to the significant efforts in improving the power conversion efficiency (PCE) to above 25%. However, the stability issue of the PSCs restricts their further development for commercialization. Strategies are designed to keep moisture and oxygen out of the perovskite films, such as additive, surface passivation, and solvent engineering; however, usually, the corrosion of active films by the residual solvent is mostly ignored. Solvent residue is the paramount factor influencing the stability of the perovskite film prepared by the solution method, and most solvents can be easily absorbed and accelerate the perovskite film decomposition. Here, we studied the residual solvent effect on two kinds of perovskite films obtained by different annealing processes: hot air annealing and hot bench annealing. Several detection techniques were used to study the performance of two different annealing methods, including time-of-flight secondary ion mass spectrometry (ToF-SIMS), thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FESEM). The perovskite film obtained by hot air annealing shows less residual solvent and better device performance than the hot bench annealing method. This method is expected to provide insight into reducing solvent residue to improve the stability of the PSCs, especially for future commercialization.

Effect of Solvent Residue in the Thin-Film Fabrication on Perovskite Solar Cell Performance.

Instability caused by the migrating ions is one of the major obstacles toward the large-scale application of metal halide perovskite optoelectronics. Inactivating mobile ions/defects via chemical passivation, e.g., amino acid treatment, is a widely accepted approach to solve that problem. To investigate the detailed interplay, L-phenylalanine (PAA), a typical amino acid, is used to modify the SnO2/MAPbI3 interface. The champion device with PAA treatment maintains 80% of its initial power conversion efficiency (PCE) when stored after 528 h in an ambient condition with the relative humidity exceeding 70%. By employing a wide-field photoluminescence imaging microscope to visualize the ion movement and calculate ionic mobility quantitatively, we propose a model for enhanced stability in perspective of suppressed ion migration. Besides, we reveal that the PAA dipole layer facilitates charge transfer at the interface, enhancing the PCE of devices. Our work may provide an in-depth understanding toward high-efficiency and stable perovskite optoelectronic devices.

Manipulating Ion Migration and Interfacial Carrier Dynamics via Amino Acid Treatment in Planar Perovskite Solar Cells.

Stable binary nanohybrids based on all‐inorganic halide perovskite encapsulated in porphyrinic Zr‐MOF (PCN‐222) are constructed for photoinduced electron transfer‐reversible addition‐fragmentation chain transfer (PET‐RAFT) polymerization. The synergistic effect of perovskite and PCN‐222 endows the photocatalyst with high‐efficiency photogenic charge carrier separation and light absorption property. CsPbI3@PCN‐222 (20%) is finally screened out as the oxygen and solvent‐resistant photocatalyst for highly efficient photo‐controlled polymerization of conjugated and unconjugated monomers under red to near infrared (NIR) light with high monomer conversion and narrow molecular weight distribution well‐defined polymers (Đ < 1.20). Controllable polymers and ultrahigh molecular weight polymers (up to 1730000 g mol−1) are successfully obtained by chain extension and block copolymerization of various monomers. The constructed photocatalysts easily achieve excellent light and temporal control, and even show high MMA conversion with NIR light under a thick barrier.

Binary Hybridization Strategy toward Stable Porphyrinic Zr‐MOF Encapsulated Perovskites as High‐Performance Heterogeneous Photocatalysts for Red to NIR Light‐Induced PET‐RAFT Polymerization

The commercialization
of perovskite solar cells is mainly limited by their operational stability. Interlayer
modification by thin interface materials between the perovskite and the charge
transport layers is one of the most effective methods to promote the efficiency
and stability of perovskite devices. However, the commonly used interlayer
materials do not meet all the demands, including good film quality, excellent
stability, and passivation capability without interfering with the charge transport.
In
this work, we propose a new material, water stable haloplumbate [TBA]PbI3
for interfacial modification, which is formed on the perovskite surface in-situ by tetra-butylammonium iodide
(TBAI) treatment. Benefiting from its passivation effect and
robustness, the modified devices result in a power conversion efficiency of 22.90%
with excellent environmental and operational stability.

Xin Jing

Papers

Water Stable Haloplumbate Modulation for Efficient and Stable Hybrid Perovskite Photovoltaics