Multifunctional Enhancement for Highly Stable and Efficient Perovskite Solar Cells

Abstract

With a certified efficiency as high as 25.2%, perovskite has taken the crown as the highest efficiency thin film solar cell material. Unfortunately, serious instability issues must be resolved before perovskite solar cells (PSCs) are commercialized. Aided by theoretical calculation, an appropriate multifunctional molecule, 2,2‐difluoropropanediamide (DFPDA), is selected to ameliorate all the instability issues. Specifically, the carbonyl groups in DFPDA form chemical bonds with Pb2+ and passivate under‐coordinated Pb2+ defects. Consequently, the perovskite crystallization rate is reduced and high‐quality films are produced with fewer defects. The amino groups not only bind with iodide to suppress ion migration but also increase the electron density on the carbonyl groups to further enhance their passivation effect. Furthermore, the fluorine groups in DFPDA form both an effective barrier on the perovskite to improve its moisture stability and a bridge between the perovskite and HTL for effective charge transport. In addition, they show an effective doping effect in the HTL to improve its carrier mobility. With the help of the combined effects of these groups in DFPDA, the PSCs with DFPDA additive achieve a champion efficiency of 22.21% and a substantially improved stability against moisture, heat, and light.

Fluoroethylamine Engineering for Effective Passivation to Attain 23.4% Efficiency Perovskite Solar Cells with Superior Stability

“…The incorporation of FEA in perovskite films changes the local bonding at the surface and boundaries. From the crystals’ results and previous reports, [ 22,33 ] the more F, the stronger the interaction with NH 2 and Pb. The most dramatic change is that the NH 2 surrounding an F site reorient toward the FEA via hydrogen bonds.…”

“…It is observed that the 1FEA has the largest recombination resistance, which is beneficial for suppressing photo‐generated charge recombination. [ 33 ] The space‐charge‐limited current (SCLC) measurements for the control, 1FEA, 2FEA, and 3FEA devices are conducted, and the results are shown in Figure 2e–h. The structure fluorine‐doped tin oxide (FTO)/TiO 2 /perovskite/PEAI/PCBM/Ag is adopted for these measurements.…”

Surface Reconstruction Engineering with Synergistic Effect of Mixed‐Salt Passivation Treatment toward Efficient and Stable Perovskite Solar Cells

“…In addition, many other kinds of passivation materials have also been reported with excellent photovoltaic performance and superior stability, such as organic molecules, polymers, ionic liquids, and Lewis acids and bases. [ 33–44 ]…”

Deep‐Level Transient Spectroscopy for Effective Passivator Selection in Perovskite Solar Cells to Attain High Efficiency over 23%

“…Recently, fluorination has been found as a facile and efficient way to improve the device performance, [8a–c] such as in organic solar cells and lead hybrid PSCs [5,8b] . When a hydrogen atom on the benzene ring is replaced by other atoms or groups, the distribution of the electron cloud on the benzene ring is changed, and thus the nucleophilic property of the benzene ring will be altered [9] .…”