Trifluoromethylphenylacetic Acid as In Situ Accelerant of Ostwald Ripening for Stable and Efficient Perovskite Solar Cells

Abstract

Perovskite thin film quality, including large grain size and low defect, is one of the fundamental factors to improve the performance and stability of perovskite solar cells (PSCs). Herein, trifluoromethylphenylacetic acid (TFPA) as the accelerant of Ostwald ripening is introduced and an in situ crystal growth control (ICGC) strategy is developed to obtain high‐quality thin films. With adding a proper amount of TFPA into the FAI/MAX (X is Br and Cl) precursor in the two‐step method, the larger grain size and reduced defect density perovskite are achieved due to Ostwald ripening. The ICGC process makes the average particle size from 476 to 625 nm. The defect density is reduced by a factor of 3.18. The high‐quality thin film endows the champion PSC (SnO2/perovskite/spiro‐OMeTAD) with a power conversion efficiency (PCE) of champion PSC higher than 22.19%. Furthermore, TFPA is insoluble in the water and thus TFPA‐modified film is resistive to moisture. The device can be stored in an argon glove box for 2000 h without efficiency change and when exposed to 65–75% relative humidity for more than 1500 h, it retains more than 85% of the initial PCE.

Perovskite Bifunctional Diode with High Photovoltaic and Electroluminescent Performance by Holistic Defect Passivation

“…The (FAPbI 3 ) 0.97 (MAPbBr 3 ) 0.03 was produced through the two-step sequential deposition method [29][30][31] with SPM to assist the growth. The bandgap, E g = 1.57 eV, was determined from the onset of Tauc plots and incident photon-to-electron conversion efficiency (IPCE) spectrum (Figures S1 and S2, Supporting Information).…”

Perovskite Surface Passivation Using Thiophene-Based Small Molecules for Efficient and Stable Solar Cells

“…15,16 After the introduction of thiophene-2-acetic acid (TCA), the positions of the two peaks of Pb have a greater shift, which indicates that −C�O in TCA and Pb 2+ ions have a strong interaction. 17 The TAA treatment further shifts the Pb 4f binding energy downward, which could be ascribed to the additional effect of forming a hydrogen bond between −NH 2 in TAA and I − in the PbI 6 2− octahedron. 18 For the XPS spectra (Figure S1), the peaks of I 3d in the TAA-treated sample also shift to lower binding energy, which may be due to the reduced formation of I vacancies by forming hydrogen bonds (N−H••• I).…”

“…After the Th treatment, the positions of the two peaks move to lower binding energy by 0.1–0.2 eV. This is attributed to the bonding of an electron-rich S atom in Th and the electron-deficient Pb 2+ ion on the perovskite surface. , After the introduction of thiophene-2-acetic acid (TCA), the positions of the two peaks of Pb have a greater shift, which indicates that −CO in TCA and Pb 2+ ions have a strong interaction . The TAA treatment further shifts the Pb 4f binding energy downward, which could be ascribed to the additional effect of forming a hydrogen bond between −NH 2 in TAA and I – in the PbI 6 2– octahedron .…”

Ambient Stable Perovskite Solar Cells through Trifluoro Acetic Acid-Mediated Multifunctional Anchoring

“…For the control device, a higher n value (closer to 2) suggests the presence of Shockley–Read–Hall recombination mechanism mostly due to deep trap states. However, the TFAA-modified device had lower n value (closer to 1) which suggests the presence of molecular or bimolecular recombination likely due to the shallow trap states. − From the log–log plot of J sc and light intensity, the α value was computed to be 0.95 and 0.98 for the control and TFAA-modified device. TFAA-modified device displayed α value closer to 1 compared to the control, suggesting minimum bimolecular or nonradiative recombinational loss .…”