Enhanced Performance of Planar Perovskite Solar Cells Induced by Van Der Waals Epitaxial Growth of Mixed Perovskite Films on WS₂ Flakes

Abstract

Organic–inorganic metal halide perovskite solar cells (PSCs) have attracted much research interest owing to their high power conversion efficiency (PCE), solution processability, and the great potential for commercialization. However, the device performance is closely related to the quality of the perovskite film and the interface properties, which cannot be easily controlled by solution processes. Here, 2D WS2 flakes with defect‐free surfaces are introduced as a template for van der Waals epitaxial growth of mixed perovskite films by solution process for the first time. The mixed perovskite films demonstrate a preferable growth along (001) direction on WS2 surfaces. In addition, the WS2/perovskite heterojunction forms a cascade energy alignment for efficient charge extraction and reduced interfacial recombination. The inverted PSCs with WS2 interlayers show high PCEs up to 21.1%, which is among the highest efficiency of inverted planar PSCs. This work demonstrates that high‐mobility 2D materials can find important applications in PSCs as well as other perovskite‐based optoelectronic devices.

Universal Passivation Strategy for the Hole Transport Layer/Perovskite Interface via an Alkali Treatment for High‐Efficiency Perovskite Solar Cells

“…Several reports have demonstrated that perovskite films preferentially textured with (110) planes reduce the surface energy, which, in turn, contributes to fewer defects, thus increasing the charge collection capability. [ 38,39 ] It has also been shown that adding additives such as MACl or caffeine to a perovskite precursor solution or introducing an interfacial layer such as WS 2 flakes as an epitaxial growth template can produce a more textured film with an increase in J sc , [ 39–41 ] similar to our observation. The presence of the interfacial layer formed by K‐Ac clearly affected the crystallographic orientation of the perovskite films, favoring enhanced charge collection with a higher J sc .…”

Dual Role of Cu‐Chalcogenide as Hole‐Transporting Layer and Interface Passivator for p–i–n Architecture Perovskite Solar Cell

“…This indicates more directional growth of perovskite on sulfur-based substrates in the 〈110〉 direction, which might be due to a more favorable growth environment due to the presence of sulfur. [25] Yin et al have shown that preferential growth of perovskite in the 〈110〉 direction can improve the hole injection to the HTL, which can be beneficial for charge collection. [26] Here it can be seen that sulfur-based surface can naturally promote the directional growth of perovskite, therefore, leading to a better interface charge transfer without increasing the cost or complexity of the fabrication process.…”

Wearable Tin‐Based Perovskite Solar Cells Achieved by a Crystallographic Size Effect

“…Yan et al. have found that perovskite is able to attain orientated growth on the WS 2 substrate by the lattice match effect between WS 2 and perovskite in one dimension [38] . Similar strategy in controlling crystallization has also been surveyed, in which Han et al.…”