The indispensable transformation to a (more) sustainable human society on this planet heavily relies on innovative technologies and advanced materials. The merits of nanoparticles (NPs) in this context are demonstrated widely during the last decades. Yet, it is believed that the impact of particle‐based nanomaterials to sustainability can be even further enhanced: taking NPs as building blocks enables the creation of more complex entities, so‐called supraparticles (SPs). Due to their evolving phenomena coupling, emergence, and colocalization, SPs enable completely new material functionalities. These new functionalities in SPs can be utilized to render six fields, essential to human life as it is conceived, more sustainable. These fields, selected based on an entropy‐rate‐related definition of sustainability, are as follows: 1) purification technologies and 2) agricultural delivery systems secure humans “fundamental needs.” 3) Energy storage and conversion, as well as 4) catalysis enable the “basic comfort.” 5) Extending materials lifetime and 6) bringing materials back in use ensure sustaining “modern life comfort.” In this review article, a perspective is provided on why and how the properties of SPs, and not simply properties of individual NPs or conventional bulk materials, may grant attractive alternative pathways in these fields.

silicon solar cell. [3][4][5][6] Pb-based halide perovskites have shown remarkable and unique PV properties compared to silicon such as tunable bandgaps, high optical absorption coefficients, balanced effective masses of electrons and holes, longer diffusion lengths, extended lifetimes of the photogenerated charge carriers, and smaller exciton binding energies. [7][8][9] Facile fabrication technology with high defect tolerance is another advantage in Pb-based halide perovskites. However, a major problem to be solved is the toxicity of the element lead (Pb) in halide perovskites, let alone moisture and air sensitivities. The toxicity issue should be solved by finding new alternative materials for substituting Pb, and one of the alternatives can be Bi 3þ -or Sb 3þ -based perovskites. Several combinations of elements together with Bi 3þ or Sb 3þ ions are proposed to be possible based on the theoretical calculations, but only a few materials have been experimentally synthesized. [10] In the case of Bi 3þ , the research focus has been devoted to Cs 2 AgBiBr 6 due to its high stability and nontoxicity. [11] Especially Cs 2 AgBiBr 6 was theoretically and experimentally tested to be a potential candidate for photovoltaic application due to its long charge carrier lifetime compared to the other potential Pbfree perovskites. [12][13][14][15][16][17] Some of the highest power conversion efficiencies (PCEs) are reported to be 2.84% [18] and 3.11%. [19] Compared to Pb-based halide perovskites, the indirect bandgap

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Nontoxic, all-inorganic perovskite light absorbers have received a great deal of attention in recent years due to their potential to replace lead-containing perovskite materials in photovoltaics. Herein, the synthesis of the lead-free double perovskite Cs2AgBiBr6 as a powder, obtained via spray-drying, is reported to be capable of paving the way toward large scale production. Upon drying of the atomized precursor solution during spray-drying, the double-perovskite phase forms by in situ crystallization. The product that is obtained from spray-drying is compared to the one that is obtained from the so-called solution cooling method, which is often used for the absorber synthesis before dissolving the double perovskite powder for the thin film deposition. The absorber powder gained from the solution cooling method sets the benchmark for the spray-dried absorber powder. XRD and Raman analyses confirm the phase purity of the double perovskite, whereas UV–Vis spectroscopy confirms the desired bandgap. Furthermore, the absorber powders from both synthesis methods are successfully used to deposit and integrate absorber films in single-junction perovskite solar cells. Besides being introduced as an alternative synthesis route for the preparation of double perovskite absorber as dry powders independently from being applied onto a given substrate, the superior advantages of spray-drying compared to the conventional synthesis of the perovskite absorber via the solution cooling method are outlined: Spray-drying not only enables the synthesis of large amounts of perovskite absorber powders but also discards the usage of precarious solvents like concentrated hydrobromic acid and thus eliminates the need for extensive safety precautions. Hence, spray-drying may help the perovskite technology take the next step toward large-scale production and commercialization.

Nickel oxide (NiOx$\left(\text{NiO}\right)_{x}$) is a promising hole transport material for perovskite/Si tandem solar cells. Various silicon cell architectures may be used as bottom cells. The polycrystalline (poly‐Si) p+false/n+$\left(\text{p}\right)^{+} / \left(\text{n}\right)^{+}$ tunnel diode is expected to be a high‐efficiency interconnection scheme between the two subcells of monolithic tandems in p‐i‐n configuration with a high thermal budget, excellent passivation properties, and low contact resistivity. However, NiOx$\left(\text{NiO}\right)_{x}$ is then interfaced to poly‐Si(p+$\left(\text{p}\right)^{+}$) and the chemical integrity of the interface due to the necessity of annealing treatments has to be questioned. For this purpose, the NiOx$\left(\text{NiO}\right)_{x}$/poly‐Si contact resistivity for different annealing temperatures is investigated between 100 and 500 °C, and two different NiOx$\left(\text{NiO}\right)_{x}$ deposition techniques, namely, wet‐chemically applied and sputter‐deposited NiOx$\left(\text{NiO}\right)_{x}$. The values of more than 1 Ω cm2$1 \textrm{ } \Omega \textrm{ } \left(\text{cm}\right)^{2}$ are obtained. The insertion of a nm‐thin metallic Ni interlayer is shown to enable a tremendous decrease of the contact resistivity by 2–3 orders of magnitude. The formation of NiSi2$\left(\text{NiSi}\right)_{2}$ is proven by highly resolved (scanning) transmission electron microscopy ((S)TEM) coupled with energy‐dispersive X‐ray spectroscopy (EDXS). This interfacial engineering approach is expected to provide an effective way of improving the contact properties and integrability of NiOx$\left(\text{NiO}\right)_{x}$ into various tandem cell processes.

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