The prospects of biologically derived materials in perovskite solar cells

• Use of biomaterials in perovskite solar cells (PSCs) is sustainable. • Biomaterials in PSCs aid waste management, biodegradability and biocompatibility. • Cellulose alters surface roughness, wettability, stability and flexibility of PSCs. • Peptides passivate defects, improve crystal quality, and charge extraction in PSCs. • Bio-derived solvents in PSCs resolve environmental, health, and safety issues. Renewable materials should be appraised for advancing the sustainability of perovskite solar cells (PSCs). In particular, emerging applications of biologically-derived materials (biomaterials) in PSCs have tremendous potential in enhancing charge transport, device performance, flexibility, long-term stability, sustainability, and circularity strategies. This review discusses the current status and identifies new research directions for biomaterials as either substitutes or composite constituents with other functional materials in charge transport layers and as solvent systems for PSCs. The current understanding of the effect of cellulose on power conversion efficiency (PCE), shape, and long-term stability of PSCs is discussed in terms of surface roughness, wettability, optical properties, defect concentration, and flexibility. Flexible PSCs that utilise biomaterials are advantageous for transportation and widespread implementation, but suffer several other possible adverse effects that lower the PCE due to decreased electron mobility from increased charge traps during bending cycles. Biomaterials have considerable scope in defect passivation, boosting PCE, and long-term stability of PSCs when applied in charge transport layers, particularly as interfacial layers between the electron transport layer and active materials.