Efficient and Stable FA‐Rich Perovskite Photovoltaics: From Material Properties to Device Optimization

Abstract

The perovskite photovoltaic field has developed rapidly within a decade. In particular, formamidinium (FA)‐rich perovskite allows a broad absorption spectrum, and is considered to be one of the most promising perovskite materials. Great progress has been achieved, and most recorded high‐efficient perovskite solar cells (PSCs) used the FA‐rich perovskite light absorption layer. However, the black α‐phase formamidinium lead iodide (FAPbI3) perovskite easily transforms into an undesirable δ‐phase at a low temperature. Thus, researchers have put a lot of effort into deeply understanding the phase transformation and stabilization mechanism of FA‐rich perovskite. Herein, the fundamental physical properties of FAPbI3 materials, including crystal structure, phase‐transition temperature, charge‐carrier dynamics, etc. are summarized, and establish a complete phase evolution with temperature by reviewing previous reports. The intrinsic and external factors are subsequently discussed for influencing the stability of FAPbI3 perovskite and the remarkable breakthroughs of FA‐rich PSCs in recent years are reviewed. Moreover, a series of strategies to stabilize FA‐rich perovskite is summarized, including but not limited to compositional engineering, passivating engineering, processing engineering, and strain engineering. Finally, several new viewpoints are provided for improving the efficiency and stability of PSCs. This review may be regarded as a reference project for preparing high‐efficient and stable perovskite photovoltaic devices.

Modulation of nucleation and crystallization in PbI2 films promoting preferential perovskite orientation growth for efficient solar cells

“…Specifically, formamidinium-rich lead iodide (FAPbI 3 ) is of interest to light absorbers because its narrow bandgap is close to the Shockley-Queisser optimum. [2][3][4][5][6][7][8][9] FAPbI 3 -based PSCs deliver extremely efficient PCEs, and their perovskite absorbers are generally prepared by a one-step antisolvent or a two-step sequential deposition method. [10][11][12][13][14][15][16] In particular, the two-step approach has excellent operability and vast potential for commercialization, thanks to the possibility of prior regulation of the lead iodide (PbI 2 ) templates.…”

Photovoltaic Performance of FAPbI3 Perovskite Is Hampered by Intrinsic Quantum Confinement

“…We focus our experimental investigation on stoichiometric FAPbI 3 films fabricated using three different solution-based processing routes. The first set of FAPbI 3 films (labeled “DMF-DMSO”) were fabricated using the standard deposition method based on neat DMF-DMSO (DMF, N , N -dimethylformamide; DMSO, dimethyl sulfoxide) solvent utilizing “antisolvent quenching” without any additives aimed at stabilizing the α-phase or slowing down the crystallization process. ,,, The second set of FAPbI 3 films (labeled “MACl route”) resulted from DMF-DMSO solution-casting involving the use of excess MACl (methylammonium chloride) as an additive to induce an intermediate phase which is easily transformed to the neat α-phase . MACl thus effectively directs the crystallization process by providing an alternative crystallization pathway and improving by improving the grain size and crystallographic purity of the fabricated film .…”

The race between complicated multiple cation/anion compositions and stabilization of FAPbI3 for halide perovskite solar cells

“…It has been reported both computationally and experimentally that the bandgap of lead halide perovskite increases with smaller monovalent cations 20,88,89 . Consequently, FAPbI 3 has a better bandgap for singlejunction outdoor solar cells at 1.45 eV, compared to MAPbI 3 at 1.52 eV, due to its larger monovalent cation size that results in higher symmetry of cubic phase and a reduced bandgap 15 , while replacing MA + with Cs + increases the bandgap to 1.73 eV 90 . Figure 2a shows the bandgap energy for a range of common perovskite materials.…”