Metal-halide perovskite solar cells combine high photovoltaic efficiency with low-temperature solution processing, but their performance and durability remain sensitive to precursor coordination, nucleation, drying, grain-boundary formation, and interfacial degradation. This critical narrative review evaluates plant-derived secondary metabolites as process-active additives rather than assuming that biological origin alone confers sustainability or passivation. Evidence is organized for alkaloids and xanthines, polyphenols and phenolic acids, and terpenoids and carotenoids, with explicit separation of experimentally demonstrated mechanisms, computational support, molecular analogy, and design hypotheses. Carbonyl-mediated coordination provides the clearest mechanistic basis for caffeine and related xanthines, whereas selected phenolic compounds have been associated, in separate studies, with coordination, crystallization control, and suppression of Sn²⁺ oxidation. Direct photovoltaic evidence now includes selected monoterpenoids, the sesquiterpene lactone artemisinin, and carotenoids, although the results remain molecule- and process-specific and do not justify class-wide generalization. The review maps molecular descriptors onto precursor chemistry, coating and crystallization variables, film structure, recombination, ion migration, device performance, and stability. Translation beyond laboratory spin coating will require specification-controlled additives, standardized stability protocols, process-compatible formulations, and iterative computational–experimental screening. This evidence-based framework identifies secondary-metabolite scaffolds as a promising but molecule-specific platform for perovskite process engineering, whose sustainability benefit remains to be established through life-cycle assessment.

The importance of conventional plastics is undeniable; however, their non-biodegradability makes them one of the biggest environmental problems. Among the alternatives to mitigate environmental damages, the production of polyhydroxyalkanoates (PHB) provides a biodegradable solution, additional to their mechanical and thermal properties, making them accessible to a wide variety of applications. In general, biopolymers accumulate as energy and carbon storage material in microorganisms such as bacteria and microalgae. In the present study, the impact of different sources like carbon, glucose, nitrogen and sodium was tested on the production of PHB in the cultures of the microalgae S. acutus . To evaluate the effect of the variables, a fractional Taguchi experimental design was devised and executed, thus, 16 experimental runs and 3 replicas in each treatment were considered. Results showed calculated concentrations of the biopolymer in a range from 7.5–34.7% w/w dry weight. Additionally, the PHB was identified by spectroscopic and thermogravimetric analysis. Statistical analysis was performed using Minitab 16, where differences in biomass production, PHB concentration in g/L and the percentage of PHB were analyzed. Likewise, a Pareto diagram was used to consider the biomass production results, with glucose, biomass-glucose, and biomass-sodium as determining factors in the PHB production. The present research provides significant data on critical factors related with PHA production, for the first time to our knowledge, thus showing Scenedesmus acutus as a PHB producer through low-cost medium providing a promising candidate for industrial scale-up.