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. 2025 Sep 19;11(38):eadv4501.
doi: 10.1126/sciadv.adv4501. Epub 2025 Sep 17.

Defect passivation and crystallization modulation in methylammonium-free wide-bandgap perovskites for all-perovskite tandem solar cells

Xuefei Jia  1 , Kaicheng Zhang  2 , Xiaofeng Gao  1 , Xufeng Liao  1 , Yujie Yang  3 , Weisheng Li  1 , Xiaojing Lv  1 , Xinyu Zhao  1 , Jiali Liu  4 , Yitong Ji  1 , Zhongliang Yan  5 , Qingguo Du  6 , Fuzhi Huang  1   7 , Zhiwei Ren  8 , Yaxin Zhai  4 , Wenchao Huang  1 , Yang Bai  5 , Canglang Yao  9 , Qianqian Lin  3 , Yi-Bing Cheng  1   7 , Jinhui Tong  1
Affiliations

Defect passivation and crystallization modulation in methylammonium-free wide-bandgap perovskites for all-perovskite tandem solar cells

Xuefei Jia et al. Sci Adv. .

Abstract

Wide-bandgap (WBG; >1.65 electron volts) perovskites based on iodine-bromine (I-Br) mixed halides are critical components of perovskite-based tandem solar cells (TSCs). However, the uncontrolled crystallization dynamics of Br-rich species lead to reduced grain sizes and high defect densities in WBG perovskite films. Herein, a multifunctional additive 3,4,5-trifluorobenzamide (TFBZ) was introduced to enhance the crystallinity and passivate defects of the methylammonium (MA)-free WBG perovskite films. The TFBZ demonstrates superior passivation capability compared to benzamide, effectively mitigating both iodine vacancies and undercoordinated Pb2+ defects via fluorine-enhanced interactions. In addition, the fluorine substituents in TFBZ could form N-H···F hydrogen bonds with formamidinium iodide to retard the crystallization rate of the perovskite. This proposed method is effective in defect passivation and crystal growth modulation for both 1.67- and 1.79-electron volt MA-free WBG perovskites, enabling the fabrication of MA-free all-perovskite TSCs with an encouraging power conversion efficiency of 29.01% (certified at 28.52%).

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Figures

Fig. 1.
Fig. 1.. Molecular structures of additives and their interaction with perovskite.
(A) Molecular structures of BZD and TFBZ. (B) Density functional theory (DFT) calculations of the adsorption energies between the FAI termination and BZD/TFBZ molecules. (C) DFT calculations of the adsorption energies between the PbI2 termination and BZD/TFBZ molecules. (D) Partial enlarged view of the Fourier transform infrared (FTIR) spectra for TFBZ and BZD, as well as their mixtures with perovskite. (E) Partial enlarged view of 1H nuclear magnetic resonance (NMR) spectra for BZD, TFBZ, and their mixtures with FAI and PbI2 in DMSO-d6 solvent. (F) X-ray photoelectron spectroscopy (XPS) spectra of Pb 4f and I 3d for perovskite films with and without TFBZ/BZD addition. a.u., arbitrary unit.
Fig. 2.
Fig. 2.. Effect of additives on the nucleation, crystallization, and morphology of perovskite films.
(A) 2D contour maps of in situ UV-vis transmission spectra for the control, w/BZD, and w/TFBZ during spin coating. (B) Top-view scanning electron microscopy (SEM) images of control, w/BZD, and w/TFBZ perovskite films. The insets show the grain size distributions. (C) Cross-sectional SEM images of control, w/BZD, and w/TFBZ perovskite films. (D) Schematic illustration of the crystallization processes in control and TFBZ-modified perovskite films. a.u., arbitrary unit.
Fig. 3.
Fig. 3.. Carrier dynamics and nonradiative recombination of WBG perovskite thin films.
(A) The pseudocolor representation of TA spectral evolution for the control, w/BZD, and w/TFBZ perovskite films. (B) Normalized surface carrier kinetics of the control, w/BZD, and w/TFBZ perovskite films photoexcited at the indicated wavelength (solid traces are nonlinear least-squares global best-fit curves). (C) Time-resolved microwave conductivity (TRMC) decays of the control, w/BZD, and w/TFBZ perovskite films. (D) Charge carrier mobilities of the control, w/BZD, and w/TFBZ perovskite films. (E) TRPL spectra of the control, w/BZD, and w/TFBZ perovskite films. a.u., arbitrary unit.
Fig. 4.
Fig. 4.. Stability of WBG perovskite thin films.
(A) PL spectra of the control, w/BZD, and w/TFBZ perovskite films under continuous illumination for different times. (B) Ion migration activation energy of the control, w/BZD, and w/TFBZ perovskite films. (C) The evolution of photographs of the WBG perovskite films stored at 25°C and under 85% relative humidity (RH). (D) Water contact angles of the control, w/BZD, and w/TFBZ perovskite films. h, hours. a.u., arbitrary unit.
Fig. 5.
Fig. 5.. Structure and performance of MA-free WBG perovskite and all-perovskite tandem devices.
(A) Cross-sectional SEM image of the 1.67-eV PSC device with the following structure: ITO/NiOx/Me-4PACz/perovskite/LiF/C60/BCP/Ag. (B) J-V curves of the best-performing devices for control, w/BZD, and w/TFBZ. (C) Statistical box plot of PCEs. (D) MPP test performed under a xenon lamp without filters at 1 sun for the encapsulated control, w/BZD, and w/TFBZ devices. (E) Ambient stability test performed under 25° ± 5°C and 20 ± 5% RH for the unencapsulated control, w/BZD, and w/TFBZ devices. (F) Cross-sectional SEM image of the MA-free all-perovskite tandem device. TRJ, tunnel recombination junction. (G) J-V curves of the best-performing all-perovskite tandem devices without and with TFBZ. (H) Comparison of PCE and VOC of the champion device achieved in this work with reported high-performance all-perovskite tandem devices (source data are from tables S12 and S13).
See this image and copyright information in PMC

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