Benzylammonium‐Mediated Formamidinium Lead Iodide Perovskite Phase Stabilization for Photovoltaics

Abstract

There is an ongoing surge of interest in the use of formamidinium (FA) lead iodide perovskites in photovoltaics due to their exceptional optoelectronic properties. However, thermodynamic instability of the desired cubic perovskite (α-FAPbI 3 ) phase at ambient conditions leads to the formation of a yellow non-perovskite (δ-FAPbI 3 ) phase that compromises its utility. A stable α-FAPbI 3 perovskite phase is achieved by employing benzylammonium iodide (BzI) and the microscopic structure is elucidated by using solid-state NMR spectroscopy and X-ray scattering measurements. Perovskite solar cells based on the FAPbI 3 (BzI) 0.25 composition achieve power conversion efficiencies exceeding 20%, which is accompanied by enhanced shelf-life and operational stability, maintaining 80% of the performance after one year at ambient conditions.

FAPbI3 Perovskite Solar Cells: From Film Morphology Regulation to Device Optimization

“…Moreover, the structure of PbI 2 almost completely followed the structure and orientation of the surrounding perovskite, making PbI 2 a possible seed for perovskite growth, as shown in Figure 3B. [49] Seol et al found that dropping the concentration of FAI from 58.2 to 40.7 mM in the two-step 2021 [100] ITO/SnO 2021 [121] FTO/TiO and 90% initial PCE after 500 h [11] ITO/NiOx/FAPbI The color of modified perovskite films appear dark after 5 weeks in ambient. [99] method could increase the surface roughness and grain size of the FAPbI 3 film.…”

“…Furthermore, with the bulk organic cations or low-dimensional perovskite assembled at the GB, high-efficiency mesoporous FAPbI 3 PSCs had been obtained. [25,[99][100][101] Especially, FAPbI 3 PSCs based on the mesoporous structure with the carbon electrode was also obtained by the printable fabrication process, which was reported to present a stability of 288 h in ambient with the 50-70% RH without encapsulation, as shown in Figure 9C. [101,102] The inverted p-i-n structure is considered to be easier to achieve robust stability due to the removal of 2 0 , 7, 7 0 -tetra-(dimethoxydiphenylamine)-spirofluorene (Spiro-OMeTAD).…”

Phase‐Pure Engineering for Efficient and Stable Formamidinium‐Based Perovskite Solar Cells

“…Long‐chain organic ammonium for the surface functionalization of 3D FAPbI 3 perovskites has been demonstrated to effectively stabilize the metastable phase‐pure FAPbI 3 . [ 164 ] To uncover the mechanism of surface‐induced phase stabilization, various organic ammonium cations involving BA + , 4‐fluorophenylethylammonium (FPEA + ), and PEA + have been investigated using surface analysis and DFT calculation. [ 165 ] The theoretical analysis result confirms that organic ammonium functionalization enables reducing the surface energy of the perovskite phase and synergistic decrease in the nanocrystal size, realizing excellent optoelectronic properties.…”

Fabrication of stable perovskite solar cells with efficiency over 20% in open air using in situ polymerized bi-functional additives

“…Sometimes, a reflection signal was not observed in the films containing FAI, suggesting the low-dimensional perovskite phases either do not form in the existence of FAI or are highly disordered, which prevents their detection. 35,36 The PbI 2 peak located at 12.68° in the sample may be ascribed to the degradation of perovskite materials caused by the escape of organic cations during the annealing procedure of the perovskite films, resulting in excessive PbI 2 being left in the perovskite precursors. 37 After the in situ crosslinking strategy, the peak intensity of PbI 2 is perceptibly reduced.…”