Work

Spontaneous Perovskite Passivator Featuring Dual Functional Groups

Year: 2026

Type: article

Abstract: A recent and potent advancement in perovskite solar cells (PSCs) is the emergence of spontaneous heterointerface modulators (SHMs), which bypasses the required additional processes of conventional heterointerface modulations. Among SHMs, alkyl-primary-ammonium-bis(trifluoromethylsulfonyl)imides (RA-TFSIs), used as hole–transport material (HTM) additives, exhibit spontaneous perovskite passivation. Upon deposition of the HTM solution containing the RA-TFSI additive, the RA cations spontaneously passivate the perovskite, exploiting the high adsorption energy of RA cations via its ammonium moiety (NH3+) over the perovskite surface. However, conventional RA-TFSIs passivate only A-site defects in perovskite crystals due to their specific passivation mechanism, which limits their effectiveness and is an intrinsic drawback of RA-TFSIs so far. Moreover, the RA components thus far have been limited; those with multiple functional groups are unprecedented. In this work, we propose a novel strategy for suppressing multiple defect sites using a spontaneous perovskite passivator featuring dual functional groups. 2-thiophene-ethyl-ammonium-TFSI (TEA-TFSI) was newly synthesized and verified as a spontaneous perovskite passivator for n-i-p-structured PSCs employing thermally stable poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA) HTM. Spontaneous perovskite passivation using the TEA-TFSI HTM additive formed a monolayer-like passivation overlayer, unlike that in conventional TEA-based passivators. The TEA cation exhibited dual-site adsorption on A-site and X-site defects via attachments of ammonium and thiophene moieties, respectively, effectively overcoming the single-site limitation of conventional RA-TFSIs. Beyond defect suppression, the TEA overlayer enhanced the physical attachment of PTAA on the perovskite. As a result, the TEA-TFSI HTM additive enhanced the photovoltaic performance of PSCs with thermal stability owing to spontaneous perovskite passivation and thereby achieved power conversion efficiency up to 22.2% and 21.7% for minicells (≈0.12 cm2) and minimodules (≈1.6 cm2, active area: 1.41 cm2), respectively. This study demonstrates a generalizable design principle for multifunctional spontaneous passivators and provides novel insights into SHM engineering for PSCs.

Source: Advanced Energy Materials

DOI: 10.1002/aenm.202506494