1. Crystal structure of perovskite^[3]

2. (a) Schematic diagram of defects in perovskite film^[10]; (b) Transition energy levels of intrinsic acceptors and intrinsic donors in MAPbI₃^[15]; (c) Schematic diagram of passivation strategies of defects

3. (a) Energy level alignment of MAPbI₃ film and PbI₂^[21]; (b) Scanning electron microscopy(SEM) image of MAPbI₃ film with PbI₂ wrapping the perovskite grain^[21]; (c) Schematic diagram of mechanism for PbI₂ passivation in CH₃NH₃PbI₃ film^[21]; (d) Schematic diagram of mechanism for K⁺ passivation^[27]; (e) Photoluminescence quantum efficiency(PLQE) of passivated perovskite thin films with increasing fraction of potassium^[27]; (f) Current density-voltage curves of the best-performing solar cells with (Cs, MA, FA) Pb(I_0.4Br_0.6)₃ absorbers without and with potassium passivation^[27]; (g) Stability for the Cs₁₀Rb₅FAPbI₃ device^[28]; (h) UV-Vis absorption spectra of the PCBM-perovskite hybrid solution^[34]

4. (a) Schematic diagram of MAPbI₃ perovskite films crystallization processes^[39]; (b) Chemical structure of caffeine^[41]; (c) Fourier Transform infrared spectroscopy (FT-IR) spectra and magnified fingerprint regions of pure caffeine, caffeine-MAPbI₃, and the pristine MAPbI₃ films^[41]; (d) FT-IR spectra of PbI₂-PMMA and pristine PMMA films^[43]; (e) Top view SEM images of perovskite films without (left) and with (right) 0.6 mg∙mL^-1 TDZDT ^[44]; (f) Photographs and schematic process for formation of FAPbI₃ perovskite films by using NMP^[45]; (g) Chemical structures of SP1, SP2 and SP3^[48]; (h) Schematic illustration of the passivation process of donor-acceptor molecules for under-coordinated Pb²⁺ cations^[48]; (i) Statistic trap densities for the control and passivated perovskite films derived from the space charge limit current (SCLC) measurement^[48]

5. (a) Schematic illustration of two neighbouring grain structures crosslinked by butylphosphonic acid 4-ammonium chloride (4-ABPACl)^[50]; (b) Surface SEM images of pristine (control) and 4-ABPA-anchored (CH₃NH₃PbI₃-ABPA) perovskite films deposited on mp-TiO₂/FTO substrates^[50]; (c) Variations of X-ray diffraction(XRD) spectra patterns of the FASnI₃-EDAI₂ 1% film at different duration of storage^[51]; (d) Schematic diagram of RATZ passivation^[53]; (e) Schematic diagram of thiophene passivation^[55]; (f) Theoretical model of perovskite with molecular surface passivation of PbI antisite with theophylline^[61]; (g) Statistical photovoltaic parameters of PCE depending on pK_a^[64]

Table 1. Additives during perovskite formation and their device performance

Table 2. Post-treatment additives and their device performance