Small Molecules with Controllable Molecular Weights Passivate Surface Defects in Air‐Stable p‐i‐n Perovskite Solar Cells

Abstract

The passivation of surface defects at the interfaces and grain boundaries of perovskites has great potential to improve the optoelectronic properties of related devices. In this study, the small molecules LG0.5, LG1.5, and LG2.5—having precise and controllable molecular weights (various generations synthesized through click reactions) and featuring urethane, urea, and malonamide functionalities—are synthesized, and their ability to passivate the defects of perovskites are evaluated. X‐ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and time‐resolved photoluminescence spectroscopy are used to observe the interactions between the perovskites and these molecules. The embedding of LG0.5 promotes the growth of large‐grain perovskite crystals, leading to increases in the intensities of the UV–vis absorption and photoluminescence spectral signals of the perovskite as well as longer carrier lifetimes. A power conversion efficiency of almost 20% for a p‐i‐n perovskite solar cell having the layer structure indium tin oxide/NiOx/CH3NH3PbI3 (with LG0.5)/[6,6]‐phenyl C61 butyric acid methyl ester/bathocuproine/Ag is observed. This device (without encapsulation) exhibits excellent air‐stability, retaining 89.8% of its initial performance after storage in an ambient environment (25 °C, 40% humidity) for over 120 d.

A multifunctional phosphorylcholine-based polymer reduces energy loss for efficient perovskite solar cells

“…For example, organic materials containing S, N, O and P atoms can work as Lewis bases to passivate the positively charged defects, such as under-coordinated Pb 2+ in perovskites. [27][28][29][30][31][32][33][34] Some highly polarized small molecules or polymers with carboxylic acid groups are also proved to be efficient passivators to modify the bulk or surface of perovskite thin films. 35,36 Zwitterionic materials are a class of unique electrolytes, where both cationic and anionic moieties are covalently tethered on the same chain.…”

Synergistic Passivation via Lewis Coordination and Electrostatic Interaction for Efficient Perovskite Solar Cells

“…The synergistic effect between functional groups known as synergistic passivation was studied to enhance this passivation. − Synergistic passivation refers to the passivation effect produced by the simultaneous action of molecules or functional groups. ,, Chemical interactions commonly used for passivation include Lewis coordination, hydrogen bond, and electrostatic interaction, and there has been some progress in the study of synergistic passivation. Recently, Wang et al found that the hydrogen bond between N–H and I can enhance the coordination passivation of the CO bond with the antisite Pb defect .…”

Understanding the PEDOT:PSS, PTAA and P3CT-X Hole-Transport-Layer-Based Inverted Perovskite Solar Cells

“…Hydrophobic NiO x - and CuO x -based thin films are also widely used in the inverted perovskite solar cells as the HTL [ 41 , 42 ]. The photovoltaic performance of NiO x -based inverted perovskite solar cells can be increased to be higher than 20% by using an organic interlayer in between the perovskite thin film and the HTL [ 43 , 44 , 45 , 46 , 47 ]. In other words, the formation of high-quality perovskite crystalline thin films is not only related to the surface wettability [ 48 , 49 , 50 ] but is also dominated by the nucleation process of perovskites on top of the organic layers.…”