The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/pssb.202100359.

Solvent–solute interactions in precursor solutions of lead halide perovskites (LHPs) critically impact the quality of solution-processed materials, as they lead to the formation of a variety of poly-iodoplumbates that act as building blocks for LHPs. The formation of [PbI2+n ] n− complexes is often expected in diluted solutions, while coordination occurring at high concentrations is not yet well understood. In a combined ab initio and experimental work, we demonstrate that the optical spectra of the quasi-one-dimensional iodoplumbate complexes PbI2(DMSO)4, Pb2I4(DMSO)6, and Pb3I6(DMSO)8 formed in dimethyl sulfoxide solutions are compatible with the spectral fingerprints measured at high lead iodide concentrations. This finding suggests that the interpretation of optical spectra of LHP precursor solutions should account for the formation of polynuclear lead halide complexes.

Lead halide perovskites (LHPs) are promising materials for opto-electronics and photovoltaics, thanks to favorable characteristics and low manufacturing costs enabled by solution processing. In light of this, it is crucial...

Lewis acids like tris(pentafluorophenyl)borane (BCF) offer promising routes for efficient p-doping of organic semiconductors. The intriguing experimental results achieved so far call for a deeper understanding of the underlying doping mechanisms. In a firstprinciples work, based on state-of-the-art density-functional theory and many-body perturbation theory, we investigate the electronic and optical properties of donor/acceptor complexes formed by quarterthiophene (4T) doped by BCF. For reference, hexafluorobenzene (C 6 F 6) and BF 3 are also investigated as dopants for 4T. Modelling the adducts as bimolecules in vacuo, we find negligible charge transfer in the ground state and frontier orbitals either segregated on opposite sides of the interface (4T:BCF) or localized on the donor (4T:BF 3 , 4T:C 6 F 6). In the optical spectrum of 4T:BCF, a charge-transfer excitation appears at lowest-energy, corresponding to the transition between the frontier states, which exhibit very small but non-vanishing wave-function overlap. In the other two adducts, the absorption is given by a superposition of the features of the constituents. Our results clarify that the intrinsic electronic interactions between donor and acceptor are not responsible for the doping mechanisms induced by BCF and related Lewis acids. Extrinsic factors, such as solvent-solute interactions, intermolecular couplings, and thermodynamic effects, have to be systematically analyzed for this purpose.

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