Clean thermal decomposition of tertiary-alkyl metal thiolates to metal sulfides: environmentally-benign, non-polar inks for solution-processed chalcopyrite solar cells

Abstract

We report the preparation of Cu2S, In2S3, CuInS2 and Cu(In,Ga)S2 semiconducting films via the spin coating and annealing of soluble tertiary-alkyl thiolate complexes. The thiolate compounds are readily prepared via the reaction of metal bases and tertiary-alkyl thiols. The thiolate complexes are soluble in common organic solvents and can be solution processed by spin coating to yield thin films. Upon thermal annealing in the range of 200–400 °C, the tertiary-alkyl thiolates decompose cleanly to yield volatile dialkyl sulfides and metal sulfide films which are free of organic residue. Analysis of the reaction byproducts strongly suggests that the decomposition proceeds via an SN1 mechanism. The composition of the films can be controlled by adjusting the amount of each metal thiolate used in the precursor solution yielding bandgaps in the range of 1.2 to 3.3 eV. The films form functioning p-n junctions when deposited in contact with CdS films prepared by the same method. Functioning solar cells are observed when such p-n junctions are prepared on transparent conducting substrates and finished by depositing electrodes with appropriate work functions. This method enables the fabrication of metal chalcogenide films on a large scale via a simple and chemically clear process.

Optimization of CuIn1–XGaXS2 Nanoparticles and Their Application in the Hole-Transporting Layer of Highly Efficient and Stable Mixed-Halide Perovskite Solar Cells

“…Therefore, the UV–vis absorption spectra (Figure b) and CV measurement (Figure d) were applied to construct energy band diagrams as shown in Figure e . The calculated energy band diagram is compatible with the literature . Varying the content of Ga element mainly contributes to the conduction band edge energies ( E CB ) compared to the valence band edge energies ( E VB ). , …”

“…50 The calculated energy band diagram is compatible with the literature. 51 Varying the content of Ga element mainly contributes to the conduction band edge energies (E CB ) compared to the valence band edge energies (E VB ). 52,53 Figure 2a demonstrates the UV−vis absorption spectra of the perovskite layer and the perovskite/CIGS double layer with different Ga percentages.…”

Polymorphic Control of Solution-Processed Cu2SnS3 Films with Thiol–Amine Ink Formulation

“…While ESI-(−)­MS is an indirect method, it is effective in gaining insights into the identities of possible molecular solutes formed in thiol–amine inks. ,, TGA has been utilized to monitor decomposition temperatures of metal thiolates, which are known to decompose over a wide temperature range (100–350 °C) depending on the identity of the metal (e.g., Cu, Sn, In, etc.) and thiol used. − Photographs of the Cu 2 S inks in EDT/en and merc/en are supplied as insets of Figure a,b, showing major color differences between the two, with the EDT/en ink being dark orange/brown and the merc/en ink being virtually colorless. Direct-injection ESI-(−)­MS was conducted to gain insights into the differences in the molecular solutes resulting from Cu 2 S dissolution in EDT/en and merc/en.…”

Defect-Inducedin SituAtomic Doping in Transition Metal Dichalcogenides via Liquid-Phase Synthesis toward Efficient Electrochemical Activity

“…The spin-cast vacancy-modulated Mo(TDT) x thin film was preannealed at 300 °C for 1 h to remove the alkyl group in the TDT, thus leaving the molybdenum and sulfur only, which was progressed via an S N 1 reaction by forming volatile dialkyl sulfide through the electrostatic attraction of carbocation intermediates and nucleophile thiolate anions. 30 As the alkyl group in the TDT was completely removed, the crystallized MoS 2 thin film was finally formed through further annealing treatments at elevated temperatures (400−600 °C), where the degree of crystallinity is controlled by the annealing temperature.…”