Ternary solvent for CH₃NH₃PbI₃ perovskite films with uniform domain size

Abstract

A ternary solvent system consisting of dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL) and N-methyl-2-pyrrolidone (NMP) has been developed to improve the uniformity of CHNHPbI (MAPbI) perovskite domains. Compared to MAPbI perovskite films prepared using a binary solvent consisting of DMSO and GBL, the surface roughness and uniformity of MAPbI films fabricated by using the ternary solvent system are greatly improved. The thermogravimetric analysis reveals that a NMP-PbI-MAI intermediate, a DMSO-PbI-MAI intermediate and MAPbI crystals co-existed in the as-cast MAPbI films. Furthermore, it is found that the thermal stability of intermediate phases and the solvent evaporation rate are critical for the nucleation of the perovskite crystals during the thermal annealing treatment. The thermally stable intermediates prepared with the ternary solvent are converted to MAPbI films with a highly uniform and smooth surface. The film forms an intimate contact with the charge transporting layer when the layer is applied as a photoactive layer in the solar cell. As a result, the power conversion efficiency of ternary solvent processed solar cells is enhanced by 38.2% compared to that of the binary solvent processed one. Furthermore, the stability of the ternary processed perovskite solar cells is greatly improved, as well. This investigation provides a better understanding about the role of different processing solvents or additives in effecting the perovskite film quality.

Dual Functions of Crystallization Control and Defect Passivation Enabled by an Ionic Compensation Strategy for Stable and High-Efficient Perovskite Solar Cells

“…23 Xie et al introduced a ternary solvent system to fabricate uniform perovskite films with less surface roughness, leading to improved PCE (18.6%) and stability. 24 Meng et al introduced thiourea as Lewis bases, which can promote the perovskite grain growth and improve the quality of perovskite films. 25 However, thiourea is an insulator and a has high boiling point.…”

“…23 The grain boundaries are the channels for oxygen transport that lead to significant decrease in charge transport properties of the perovskite films. 24 According to the coordination chemistry, various intermediate groups exist in the perovskite precursor solution, including [PbIL 5 ] + (L is ligand), [PbI 2 L 4 ], [PbI 3 L 3 ] − , [PbI 4 L 2 ] 2− , [PbI 5 L 1 ] 3− , and PbI 6 4− . 26 However, most of them produce defect states during the formation of perovskite crystals except the fully coordinated PbI 6 4− .…”

Effects of the additives n-propylammonium or n-butylammonium iodide on the performance of perovskite solar cells

“…The crystallization behaviour of the perovskite thin lms controls the development of surface topography, which affects the charge separation, recombination mechanics, and diffusion-length of perovskite thin lms. Key factors, including deposition method, surrounding, precursor composition, solvent, [15][16][17][18][19][20][21] and the additives used, control the crystallization process. 18,[22][23][24][25][26][27][28] PSCs with a PCE of more than 20% relied on process modication and material engineering.…”

“…Key factors, including deposition method, surrounding, precursor composition, solvent, [15][16][17][18][19][20][21] and the additives used, control the crystallization process. 18,[22][23][24][25][26][27][28] PSCs with a PCE of more than 20% relied on process modication and material engineering. 29 Using a simple perovskite solution deposition method, the mesoporous scaffold provides physical limitations on the size of the perovskite crystals to achieve the desired quality of the relative thickness lm.…”

Additive Engineering for Efficient and Stable MAPbI3-Perovskite Solar Cells with an Efficiency of over 21%

“…This shows that MAOCN can effectively prolong the existence time of the PbI 2 (NMP) phase and help improve the crystalline quality of PbI 2 . At the same time, as shown in Figure S3b–d, compared with the unannealed perovskite film, the unannealed perovskite/MAOCN film has a stronger CH 3 NH 3 I-NMP-PbI 2 intermediate phase peak, and the annealed perovskite/MAOCN film has a stronger (110) perovskite peak . In addition, for either PbI 2 or perovskite films, no additional characteristic peaks appear after the addition of MAOCN, which indicates that the dominant intermediate phases in the unannealed PbI 2 and perovskite films are PbI 2 (NMP) and CH 3 NH 3 I-NMP-PbI 2 phases, respectively.…”