Achieving Reproducible and High-Efficiency (>21%) Perovskite Solar Cells with a Presynthesized FAPbI₃ Powder

Abstract

The conventional precursor mixture based on highly pure and expensive PbI2 (purity >99.99%) is problematic in commercializing perovskite solar cells (PSCs) because of a large deviation in the batch-to-batch photovoltaic performance due to underlying nonstoichiometry and/or the nonperovskite phase. Here, we report on reproducibly efficient (>21%) PSCs based on the ambient-temperature-stable δ-phase FAPbI3 powder, synthesized by reacting PbI2 (either homemade or low-grade commercial product with purity <99%) with formamidinium iodide (FAI) at room temperature (∼93% yield). X-ray diffraction patterns confirm that annealing the spin-coated film leads to phase purity of cubic α FAPbI3. As compared to the conventional precursor mixture based on PbI2 (purity = 99.9985%), significantly reducing defects in the powder-based film is responsible for the stable and reproducible efficiency. In addition, the homogeneous light-intensity-dependent surface photocurrent contributes to the reproducibility of photovoltaic performance. The quasi-steady-state power conversion efficiency of 21.07% is certified for the device based on FAPbI3 powder.

Effect of Additives AX (A = FA, MA, Cs, Rb, NH4, X = Cl, Br, I) in FAPbI3 on Photovoltaic Parameters of Perovskite Solar Cells

“…FAPbI 3 powder was synthesized according to our method reported in previous studies. [ 20 ] FAI (2.236 g) was reacted with PbI 2 (4.61 g) (molar ratio FAI:PbI 2 = 1.3:1) in 60 mL ACN under stirring for 2 days. The supernatant was removed and 8 mL of fresh ACN was added to the product, which was stirred for 15 min to wash the product.…”

“…In this Report, we systematically study the effect of cation and/or anion in additives using FAX (X = Cl, Br, and I) and ACl (A = FA, MA, Cs, Rb, NH 4 ) on photovoltaic parameters and optoelectronic properties of PSCs. For this purpose, we used a presynthesized FAPbI 3 powder [ 20 ] as precursor material, to which the additives were introduced with different concentrations to find optimal molar ratio. With seven additives, photovoltaic parameters were found to depend both cations and anions in the halide additives.…”

Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells

“…[ 29 ] Among them, inorganic external additives were recently exploited. Chloride incorporated as MACl [ 30 ] or as methylendiammonium dichloride (MDACl 2 ), [ 31 ] or PbS QDs confer outstanding stability to the FA‐based perovskite, without affecting its bandgap. [ 32 ] Beyond that, inorganic PbS quantum dots (QDs) with similar lattice parameter are incorporated into the perovskite matrix for a bulk‐epitaxial growth of the perovskite.…”

Recent Advances and Perspectives on Powder‐Based Halide Perovskite Film Processing

“…[ 58 ] For the synthesis of FAPbI 3 via precipitation it was found to be sufficient, to dissolve FAI in acetonitrile, add PbI 2 and stir this solution for 24 h to precipitate the perovskite (Figure 2d). [ 41 ] The shape of the resulting perovskite particles can be influenced by the solvents and by adding longer‐chain organic ions. For example, adding toluene to a solution of PbI 2 and MAI in acetonitrile results in precipitation of cubic MAPbI 3 particles.…”