Fig. 1. Roles of natural biomaterials in PeSCs. ETL：electron transport layer；HTL：hole transport layer^［50-55］

Fig. 2. （a）Morphology images of perovskite films with and without caffeine，（b）normalized azimuth angle plots along（110）crystal plane from the 2D grazing incidence wide-angle X-ray diffraction patterns of perovskite films with and without caffeine，（c）J-V curves of PeSCs with and without caffeine，（d）normalized PCE decays upon 85 ℃ continuous annealing in nitrogen box^［58］

Fig. 3. （a）The crystallization process of perovskite films with and without EC under 100 °C annealing，（b）top-view SEM images of perovskite films with different EC concentrations，（c）the schematic diagram of the long-chain EC scaffold against expansion/shrinkage stress，^［49］（d）chemical structure of M13 bacteriophage with multiple functional groups，（e）working mechanism of M13 bacteriophage-templated perovskite crystal growth，（f）PCE statistical analysis of PeSCs with M13 bacteriophage under different heat treatment^［50］

Fig. 4. （a）The schematic illumination of the interactions between forested-based biomaterial betulin and perovskite，（b）J-V curves of PeSCs with and without betulin under forward and reverse scan，^［51］ charge density distribution of MAPbI₃（001）surface（c）with no defect，（d）with Pb-I antisite defect and（e）with Pb-I antisite defect after PLL passivating，density of states of MAPbI₃（001）surface（f）with no defect，（g）with Pb-I antisite defect and（h）with Pb-I antisite defect after PLL passivating^［66］

Fig. 5. （a）Chemical structure of natural amino acids（NAAs）molecules including glycine（Gly），glutamic acid（Glu），proline（Pro），and arginine（Arg），（b）steady-state and（c）time-resolved photoluminescence（PL）spectra of the pristine and various NAAs-passivated perovskite films，^［67］（d）interaction structures of perovskite and theophylline，caffeine，and theobromine with corresponding theoretical interaction energy，（e）J-V curves of PeSCs with or without biomaterials’ treatment under reverse scan direction，（f）normalized PCE decays of encapsulated PeSCs with or without theophylline treatment under continuous light（90 ± 10 mWcm^-2）exposure^［48］

Fig. 6. （a）UPS spectra of secondary electron cutoff region and valence band region of PTAA：F4TCNQ，pristine perovskite and capsaicin-containing perovskite deposited on PTAA：F4TCNQ，（b）energy levels of perovskite with and without the capsaicin derived from UPS spectra，（c）cross-sectional AFM topographies，corresponding KPFM images，and potential profiles under zero-voltage bias of perovskite-capsaicin/PTAA：F4TCNQ/ITO，（d）J-V curves of PeSCs with or without the capsaicin under reverse and forward scan directions，（e）recent works on polycrystalline based and single-crystal MAPbI₃-based p-i-n PeSCs，（f）evolution of the PCEs measured from unencapsulated PeSCs in ambient air with 45% relative humidity（RH）at room temperature（RT），^［77］（g）UPS spectra of secondary electron cutoff region（left panel），LEIPS spectra of valence band region（middle panel），and LEIPS spectra of conduction band region（right panel）of the perovskite films with and without the carnitine，（h）the schematic illustration of the energy levels of PeSCs with and without carnitine^［78］

Fig. 7. （a）Cross-section SEM image of PeSCs with HS modified TiO₂，top-view SEM images of：（b）pristine and HS-modified TiO₂，and（c）perovskite films deposited on pristine and HS-modified TiO₂ substrates，J–V characteristics of PeSCs（d）without and（e）with HS layers under forward and reverse scan directions，（f）stability test of PeSCs without and with HS interlayers in N₂ and ambient environment，^［91］（g）the schematic illumination of the interaction mechanism between DNA and meso-TiO₂，（h）the surface potential curves of undoped and DNA doped meso-TiO₂^［92］

Fig. 8. （a）Device structure of the bio-PeSCs，（b）the schematics of the FRET process between perovskite and bR，（c）band alignment of the bio-PeSCs，（d）J-V curves of PeSCs with and without bR modification^［53］

Fig. 9. （a）The schematic interactions of dopamine with perovskite and TiO₂ interface，（b）energy level diagram，（c）the normalized PCE change of PeSCs with TiO₂ and dopamine-capped TiO₂ as ETLs kept under continuous full-sun illumination in nitrogen atmosphere^［93］，（d）photographs and（e）Pb release concentrations of PeSCs with different HAP contents after the immersion in water for 0-24 h^［95］

Fig. 10. （a）Dipole effect of creatine layer at the perovskite/SnO₂ interface，（b）defect passivation ability of the creatine layer，（c）energy level illustration of the UPS results，^［100］（d）the schematic of device structure with Isatin and Isatin-Cl as cathode interlayer，（e）the energy level diagram，（f）J-V curves of pristine，Isatin and Isatin-Cl optimized devices under forward and reverse scan directions^［84］

Fig. 11. （a）Molecular structures of zinc chlorophyll aggregates，Chl-1 and Chl-2，（b）the energy level diagram of PeSCs based on Chl-1，Chl-2，and P3HT as HTLs，（c）time-resolved PL decays，^［104］（d）UPS spectra for NiO_x film before and after adenine modification，（e）the energy diagram of the device，（f）J-V curves of control and adenine-modified devices under forward and reverse scan directions^［54］

Fig. 12. （a）Synthesis condition，copolymer of DA-PEDOT：PSS，and energy levels of PEDOT：PSS and DA-PEDOT：PSS in PeSCs，^［109］（b）considerable differences in doping of PEDOT：PSS and DA-PEDOT：PSS，（c）ESR spectra of PEDOT：PSS and DA-PEDOT：PSS at room temperature and 373 K，respectively，（d）J–V curves of PEDOT：PSS and DA-modified PEDOT：PSS based PeSCs，（e）long-term stability of PeSCs with PEDOT：PSS and DA-modified PEDOT：PSS HTLs in air under ambient conditions（temperature ≈ 25 ℃，humidity ≈ 40%）^［110］

Fig. 13. （a）Device structure of paper based HTM-free PeSCs and（b）corresponding energy level diagram，（c）photovoltaic performance of paper based HTM-free PeSCs under forward and reverse scan directions，（d）J-V curves of paper based device with different bending cycles，（e）optical image of paper based HTM-free PeSCs attached on the wrist and（f）bent with radius（R）of 6 mm^［113］

Fig. 14. （a）Preparation process of bamboo-derived cellulose nanofibril（b-CNF）electrodes，（b）photographs of b-CNF/IZO electrode recovery from random crumpling，（c）square resistance of b-CNF/IZO and PET/IZO electrode bending at different curvature radii，（d）the main parameters’ variation of the flexible PeSCs upon periodic bending tests of a 4 mm curvature radius^［55］

Fig. 15. （a）The schematic illustration of preparation process of M13 bacteriophage-templated gold nanowire electrode，（b）illustrations of the virus-templated Au nanowires on PDMS with PTAA and perovskite layers，（c）stretchable ability test of M13 virus-templated Au nanowire electrode，（d）stretchable ability test of M13 virus-templated Au nanowire-based PeSCs^［114］