Fig. 1. (Color online) Crystal structure diagram for the perovskite material^[4].

Fig. 2. (Color online) Absorption coefficients over photon energy for perovskite, GaAs, and single crystal silicon^[8].

Fig. 3. (Color online) Current–voltage performance of a PSC with (a) hysteresis properties and (b) no hysteresis properties. (c) Schematic diagram denoting potential causes of hysteresis in a PSC^[15].

Fig. 4. (Color online) Time lapse of perovskite film degradation due to humidity^[22].

Fig. 5. (Color online) Stability depicted by change in absorption of perovskite films for two days in (a) illuminated, nitrogen atmosphere, (b) dark, nitrogen atmosphere, (c) illuminated, ambient atmosphere^[27].

Fig. 6. (Color online) Effect of UV light stability due to percentage of bromide included in PSC^[31].

Fig. 7. (Color online) Encapsulation methods for PSCs (a) with a full covering of epoxy and (b) with a ‘u’-shaped glass cover and a desiccant^[33].

Fig. 8. (Color online) Three common examples of 2D perovskites as the active layer of PSCs^[38].

Fig. 9. (Color online) Crystal Structures of Ruddlesden-Popper and Dion-Jacobson perovskites^[38].

Fig. 10. (Color online) Crystal structure for Ruddlesden-Popper perovskites with increasing ‘n’ values^[40].

Fig. 11. (Color online) Growth orientations of Ruddlesden-Popper perovskites: horizontal and vertical^[38].

Fig. 12. (Color online) Solvent effect on growth direction for pure DMF, equal parts DMF and DMSO, and pure DMSO^[36].

Fig. 13. (Color online) Normalized efficiency of BA RPPSCs over time with (a) constant illumination while unencapsulated, (b) unencapsulated in humidity, (c) constant illumination while encapsulated, and (d) encapsulated in humidity^[49].

Fig. 14. (Color online) Energy payback times per photovoltaic material where P-1 and P-2 are two PSCs with different layers^[54].

Fig. 15. (Color online) (a) Sequential processing of R2R production for all steps. (b) Slot die printing apparatus. (c) Resulting fPSC device. (d) Razza et al.’s R2R processing apparatus^[59].

Fig. 16. (Color online) fPSC device structure of Han et al. on titanium film^[67].

Fig. 17. (Color online) (a) Schematic view of PEN sandwich set-up for (a1) single PEN, (a2) double PEN with 125 μm offset, and (a3) double PEN with neutral position. (b–d) SEM images of PEN devices post flexing with a higher magnification on apparent cracks. The images correspond with the schematic set-up as follows: (b) is (a1), (c) is (a2), and (d) is (a3)^[76].

Fig. 18. SEM Images of (a) ITO on PET with ITO flexed outward and inward, (b) ITO on CPI with ITO flexed outward and inward^[71].

Fig. 19. (Color online) Perovskite film deposition method by Wu et al. with spin-coating, low pressure solvent removal, and thermal annealing^[70].

Fig. 20. Device structure of inverted fPSC with an efficiency of 18.1% ITO/PET/perovskite/fullerene/BCP/Copper^[81].

Fig. 21. (Color online) (a1) Cell structure with energy band levels. (a2) Slot die set-up with gas quenching attachment. (b) Roll to Roll manufacturing set-up seen in stages (b1) PbI₂ deposited (b2) PbI₂ layer annealed with gas quenching (b3) resulting film after MAI^[84].

Fig. 22. (Color online) (a) Perovskite deposition method by Zuo et al. where solution is deposited onto a heated substrate and quenched with nitrogen gas then heated with a second hot plate. (b) Photographs of resulting rolls^[85].

Fig. 23. (Color online) Conversion of 1 lead-acid battery into 709 m² PSCs and power for 30.2 homes in Las Vegas^[93].

Fig. 24. (Color online) Refining processes for PbI₂ in perovskite solar cells when harvest from raw lead ore or car batteries^[93].

Fig. 25. (Color online) Two-step process of Kim et al. to extract lead from solvents^[94].

Fig. 26. (Color online) Environmental Profile of FTO/TiO₂/perovskite/spiro/Au focus should be given to the factors highlighted with a red box^[54].

Fig. 27. (Color online) Environmental profile of ITO/ZnO/perovskite/Ag^[54].

Fig. 28. (Color online) Holistic impact of various PV materials on resources, human health, and ecosystem quality P-1 is FTO/ TiO₂/perovskite/spiro/Au P-2 is ITO/ZnO/perovskite/Ag^[54].

Table 1. Summary of flexible substrates with their maximum working temperature, cost, and record efficiency.