FAPbI₃ Perovskite Films Prepared by Solvent Self-Volatilization for Photovoltaic Applications

Abstract

Developing a simple method to synthesize the perovskite layer without the antisolvent technique can facilitate the industrial production of perovskite solar cells (PSCs). Limited progress has been made for the antisolvent-free method on formamidinium lead triiodide perovskite layers because of the phase stability issue. Here, we use N-methyl pyrrolidone (NMP) as an additive to inhibit the nonperovskite phase of FAPbI 3 to fabricate the formamidinium iodide (FAI)−PbI 2 −NMP intermediate phase via the self-volatilization of volatile solvent 2-methoxyethanol instead of the traditional antisolvent method. The high-quality pure α phase of FAPbI 3 films is obtained by phase transition via annealing. The photovoltaic properties of the perovskite films affected by different NMP amounts are studied. The corresponding PSCs show a PCE of 20.1% compared to 15.6% for the PSCs fabricated with the classical antisolvent technique. The unencapsulated devices exhibit ∼75% efficiency of their initial PCE values after 35 days of storage. This method can be used in the scalable production of PSCs because of high reproducibility and easy operation.

Molecular design for perovskite solar cells

“…The halide perovskite precursor solutions are rich in tunable organic molecules, including the precursors, the additives, and the solvent molecules; these are all closely related to the coordination chemistry of the functional molecules and strongly affect the resulting perovskite film quality. Many efforts have been devoted to modifying the precursor solution, additives, and solvents, such as on those for FAPbI 3 preparation, 56‐58 additive MACl, 59‐62 ionic liquid, 63‐65 and MAPbBr 3 quantum dots 66‐68 . For example, the AX and BX 2 precursors in the precursor solution are essentially in the molecular form at the starting point, and non‐stoichiometric precursors are viable to generate improved perovskite film quality; the unreacted PbI 2 is suggested to improve the perovskite film crystallinity 69‐71 and facilitate the electron transfer to the neighboring TiO 2 layer.…”

Green-solvent-processed formamidinium-based perovskite solar cells with uniform grain growth and strengthened interfacial contact via a nanostructured tin oxide layer

“…20 Besides DMSO, 2-methoxyethanol (2-Me) with lower toxicity was also used to replace DMF in many large-area fabrication processes of PSCs. [21][22][23][24][25][26] Without strong coordination ability, 2-Me often requires other toxic solvent additives, such as acetonitrile (ACN) 22 and N-methylpyrrolidone (NMP), 23 to achieve a desirable film morphology and device performance. Recently, a new family of greener solvents, triethyl phosphate (TEP) and trimethyl phosphate (TMP), 27,28 show comparable dissolving ability for perovskite precursors.…”

Binary Microcrystal Additives Enabled Antisolvent‐Free Perovskite Solar Cells with High Efficiency and Stability

“…Organic-inorganic metal halide perovskite solar cells (PVSCs) have attracted enormous attention in the past decade due to their rapidly increasing power conversion efficiency (PCE) over including gas flow, [18][19][20] low-pressure suction, [21,22] sequential deposition, [23][24][25] solvent engineering, [26][27][28] and additive coordination. [29,30] For example, Huang et al used an air-knife to accelerate the evaporation of residual solvents from bladecoated films, which allows a PCE of 23.6% to be achieved for inverted PVSCs.…”

“…As a result, there is a strong push for searching antisolvent‐free techniques to facilitate swift solvent evaporation and effective tuning of crystallization dynamics of perovskites, including gas flow, [ 18–20 ] low‐pressure suction, [ 21,22 ] sequential deposition, [ 23–25 ] solvent engineering, [ 26–28 ] and additive coordination. [ 29,30 ] For example, Huang et al used an air‐knife to accelerate the evaporation of residual solvents from blade‐coated films, which allows a PCE of 23.6% to be achieved for inverted PVSCs.…”