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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