Surface‐Anchored Acetylcholine Regulates Band‐Edge States and Suppresses Ion Migration in a 21%‐Efficient Quadruple‐Cation Perovskite Solar Cell

Abstract

Although incorporating multiple halogen (bromine) anions and alkali (rubidium) cations can improve the open‐circuit voltage (Voc) of perovskite solar cells (PSCs), severe voltage loss and poor stability have remained pivotal limitations to their further commercialization. In this study, acetylcholine (ACh+) is anchored to the surface of a quadruple‐cation perovskite to provide additional electron states near the valence band maximum of the perovskite surface, thereby enhancing the band alignment and minimizing the Voc loss significantly. Moreover, the quaternary ammonium and carbonyl units of ACh+ passivate the antisite and vacancy defects of the organic/inorganic hybrid perovskite. Because of strong interactions between ACh+ and the perovskite, the formation of lead clusters and the migration of halogen anions in the perovskite film are suppressed. As a result, the device prepared with ACh+ post‐treatment delivers a power conversion efficiency (PCE) (21.56%) and a value of Voc (1.21 V) that are much higher than those of the pristine device, along with a twofold decrease in the hysteresis index. After storage for 720 h in humid air, the device subjected to ACh+ treatment maintained 70% of its initial PCE. Thus, post‐treatment with ACh+ appears to be a useful strategy for preparing efficient and stable PSCs.

Mixed dimensionality of 2D/3D heterojunctions for improving charge transport and long-term stability in high-efficiency 1.63 eV bandgap perovskite solar cells

“…1b, in which the 3D wide-bandgap perovskite system is Rb 0.05 Cs 0.05 (FAPbI 3 ) 0.83 (MAPbBr 3 ) 0.17 (bandgap = 1.63 eV) prepared from a one-step anti-solvent method, following our previous reports. 36,37…”

Simultaneous Bulk and Surface Defect Passivation for Efficient Inverted Perovskite Solar Cells

“…Under the synergistic effects of the additive and surface-modification agent, the TIDP film reveals both large grain size and smoother surface morphology (with the roughness of 17.2 nm), thus facilitating the charge transport process in the bulk perovskite film and the carrier extraction process at the interface simultaneously. 31,32 Then, X-ray diffraction (XRD) patterns were measured to explore the impact of trometamol molecules on the crystallinity of perovskite films. As illustrated in Figure 4a, the BP film exhibits remarkably enhanced diffraction peaks of 14.2°and 28.5°, which are assigned to diffraction from (110) and (220) planes.…”

“…To further confirm the beneficial effects of the TIDP strategy on the defect passivation process, the space charge limited current (SCLC) method was employed to quantify the defect density by means of the device architecture of ITO/ SnO 2 /MAPbI 3 /PCBM/Cu (Figure 5e). The concentration of defect density (N Trap ) is calculated according to the following equation: 31 N V qL…”

“…Meanwhile, the surface treatment by trometamol also leads to decreased film roughness for the SP film (21.2 nm) because the surface defects can be passivated efficiently during post-treatment. Under the synergistic effects of the additive and surface-modification agent, the TIDP film reveals both large grain size and smoother surface morphology (with the roughness of 17.2 nm), thus facilitating the charge transport process in the bulk perovskite film and the carrier extraction process at the interface simultaneously. , …”

“…To further confirm the beneficial effects of the TIDP strategy on the defect passivation process, the space charge limited current (SCLC) method was employed to quantify the defect density by means of the device architecture of ITO/SnO 2 /MAPbI 3 /PCBM/Cu (Figure e). The concentration of defect density ( N Trap ) is calculated according to the following equation: where ε 0 is the vacuum permittivity, ε the relative dielectric constant, q the elementary charge, and L the film thickness. Given the values of trap-filled limit voltage ( V TFL ), the N Trap values of control, BP, SP, and TIDP films were determined to be 6.23 × 10 15 , 5.52 × 10 15 , 4.25 × 10 15 , and 2.83 × 10 15 cm –3 , respectively, implying that the TIDP strategy is capable of realizing efficient defect healing in the integrated devices.…”