## 2 The Mechanisms of Additives
### Forming an Intermediate or Reacting
The carrier lifetime increased from 460.38 ns to 706.28 ns. The energy level diagram of the material is shown in Figure 20d, with the valence band moving slightly upward by about 0.07 eV. In terms of hole injection, the valence band of spiro-MeOTAD is better matched than the control perovskite film. In addition, the upshifted conduction band also facilitates electron injection into the TiO\({}_{2}\). Steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) were measured to investigate the effect of M additives on the reorganization and carrier lifetime of the perovskite film. Compared to the original perovskite, the optimized device improved V\({}_{\text{OC}}\) and FF, with an average PCE approaching a maximum of 17.32%, an increase of about 9.2% compared to the PCE of 15.86% of the original perovskite without additive treatment. Figure 19: (**a**) Schematic: crystallization process of perovskite. (**b**) Single point steady state PL spectra of ABS-0 and ABS-1 films. (**c**) Single point time-resolved photoluminescence (TRPL) spectrum of ABS-0. (**d**) Cross-sectional SEM image of a perovskite film having an optimum concentration of ABS. (**e**) J-V curve. Reproduced with permission from Reference [61]. Copyright 2019 Royal Society of Chemistry. Although many chemical additive projects produce high quality film, inherent insulating properties of chemical additives prevent the efficient transport and extraction of charge carriers. Thus, semiconductor additives have been noted. Urea and/or thiourea can be integrated as a core functional part into newly designed semiconductor chemical additives to increase the size and uniformity of the perovskite grains. However, the incorporation of urea or thiourea moieties into organic semiconductors requires a large amount of synthetic effort and often leads to a significant decrease in charge carrier mobility. Therefore, [PERSON] et al. [63] used Rhodamine as a core operative part of semiconductor chemical additives. Furthermore, the effect of the conjugated organic molecule (SA-1, SA-2), which has a rhodamine moiety, as shown in Figure 21a, as a semiconductor chemical additive on the perovskite film formation was further explored. Figure 21b shows a SEM image of the resulting perovskite film. It is noteworthy that a significant increase in the perovskite grain size based on MAPbI\({}_{3}\) and FA\({}_{0.8}\) MA\({}_{0.2}\)Pb(I\({}_{0.8}\)Br\({}_{0.2}\))\({}_{3}\) was observed in the film treated with SA-1.This may be due to the Lewis acid-base interaction between the rhodamine fraction of SA-1 and the perovskite precursor, which may increase the free energy of the critical Gibbs nucleation. Therefore, relatively few nuclei are formed, which leads to a considerable increase in the size of the perovskite grains. The SEM image of the perovskite with SA-2 also showed an increase in the size of the grains, indicating that the tertiary amine moiety did not significantly affect the Lewis acid-base interaction between the rhodamine moiety and the perovskite precursor. Figure 21c shows the J-V curve for the best performance device using SA material. Among them, the PCE with SA-2 was the highest, at 20.3%. Figure 20: (**a**) Chemical structure of melamine. (**b**) PL and (**c**) TRPL spectra of perovskites. (**d**) Energy level diagram of the material. (**e**) Short-circuit current density (J\({}_{\text{SC}}\)), (**f**) fill factor (FF), (**g**) open circuit voltage (V\({}_{\text{OC}}\)) and (**h**) power conversion efficiency (PCE) photovoltaic statistical parameters. Reproduced with permission from Reference [62]. Copyright 2018 American Chemical Society.