The Role of SnF₂ Additive on Interface Formation in All Lead‐Free FASnI₃ Perovskite Solar Cells

Abstract

Tin-based perovskites are promising alternative absorber materials for leadfree perovskite solar cells but need strategies to avoid fast tin (Sn) oxidation. Generally, this reaction can be slowed down by the addition of tin fluoride (SnF 2 ) to the perovskite precursor solution, which also improves the perovskite layer morphology. Here, this work analyzes the spatial distribution of the additive within formamidinium tin triiodide (FASnI 3 ) films deposited on top of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transporting layers. Employing time-of-flight secondary ion mass spectrometry and a combination of hard and soft X-ray photoelectron spectroscopy, it is found that SnF 2 preferably accumulates at the PEDOT:PSS/perovskite interface, accompanied by the formation of an ultrathin SnS interlayer with an effective thickness of ≈1.2 nm.

Capping Ligand Engineering Enables Stable CsPbBr3 Perovskite Quantum Dots toward White-Light-Emitting Diodes

“…41 Ahmed et al achieved excellent optical properties by surface ligand modification of CsPbBr 3 with tetrafluoroborate salt, which effectively suppressed surface defects and oxidation. 42 Zillner et al speculated that fluorine could delay the oxidation of Sn, 43 similar to the view of Zhang et al who inferred that fluorine formed a fluorine-rich environment on the surface of PeQDs, creating chemically stable Sn−F coordination 44 and hindering the electron transfer from Sn 2+ to oxygen during long-term operation. 45 However, in practical production, processing PeQDs by twostep ligand engineering via thermal injection is still complex and time-consuming.…”

Prospects for Tin-Containing Halide Perovskite Photovoltaics

“…In addition, the currently employed additive mixtures may be optimized for PEDOT:PSS, and the requirements on SAM layers may be different. FASnI 3 specifically has been shown to form an interfacial SnS (tin sulfide) phase at the buried interface with PEDOT:PSS, which was not observed for mixed Sn–Pb, but other beneficial reactivity may occur …”

“…FASnI 3 specifically has been shown to form an interfacial SnS (tin sulfide) phase at the buried interface with PEDOT:PSS, which was not observed for mixed Sn−Pb, but other beneficial reactivity may occur. 151 Besides the HTL, the ETL interface is also critical in determining the performance of PSCs, particularly the V OC . For Sn-containing PSCs, the most common ETLs are the fullerenes C 60 and PCBM (phenyl-C 61 -butyric acid methyl ester), owing to their good conductivity and reasonable alignment.…”

“…FASnI 3 specifically has been shown to form an interfacial SnS (tin sulfide) phase at the buried interface with PEDOT:PSS, which was not observed for mixed Sn–Pb, but other beneficial reactivity may occur. 151 …”

Efficient Tin (II) Fluoride‐Free Formamidinium Tin Triiodide Perovskite Solar Cells via Composition and Additive Engineering

“…[43][44][45][46][47][48][49][50] However, the loading of SnF 2 is a double-edged sword, which can easily cause phase separation of perovskites and result in SnS impurities at the poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS)/perovskite interface and would limit the further performance enhancements of the devices. [51,52] Therefore, realizing efficient TPSCs through facile composition and additive engineering remains a substantial challenge.…”