Interfacial Engineering at the 2D/3D Heterojunction for High-Performance Perovskite Solar Cells

Abstract

Perovskite solar cells based on two-dimensional/three-dimensional (2D/3D) hierarchical structure have attracted significant attention in recent years due to their promising photovoltaic performance and stability. However, obtaining a detailed understanding of interfacial mechanism at the 2D/3D heterojunction, for example, the ligand-chemistrydependent nature of the 2D/3D heterojunction and its influence on charge collection and the final photovoltaic outcome, is not yet fully developed. Here we demonstrate the underlying 3D phase templates growth of quantum wells (QWs) within a 2D capping layer, which is further influenced by the fluorination of spacers and compositional engineering in terms of thickness distribution and orientation. Better QW alignment and faster dynamics of charge transfer at the 2D/3D heterojunction result in higher charge mobility and lower charge recombination loss, largely explaining the significant improvements in charge collection and open-circuit voltage (V OC ) in complete solar cells. As a result, 2D/3D solar cells with a power-conversion efficiency of 21.15% were achieved, significantly higher than the 3D counterpart (19.02%). This work provides key missing information on how interfacial engineering influences the desirable electronic properties of the 2D/3D hierarchical films and device performance via ligand chemistry and compositional engineering in the QW layer.

Double‐Sided Surface Passivation of 3D Perovskite Film for High‐Efficiency Mixed‐Dimensional Perovskite Solar Cells

“…Enhanced crystallinity and lower surface strain with 1 mg mL −1 n‐ BAI concentration may contribute to the enhanced FF of the corresponding PSCs. The absence of an observable 2D perovskite peak for the optimum n‐ BAI concentration of 1 mg mL −1 may also support previous reports, suggesting that the formation of the 2D perovskite phase is not essential for enhanced device performance; rather that the unconverted halide layer itself may provide effective surface passivation, reduce surface strain, and enhance 3D perovskite crystallinity.…”

3D/2D Bilayerd Perovskite Solar Cells with an Enhanced Stability and Performance

“…Organic salt, composed of bulky organic cations and counter halide (see Section 4 . Organic salt for 2D perovskite for details), is dissolved in isopropyl alcohol (IPA) [ 24 , 25 , 26 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ] or chlorobenzene (CB) [ 36 , 42 ] and dripped on the surface of a spinning 3D perovskite film, whose excess PbI 2 readily reacts with the organic salt, leading to the formation of a 2D capping layer on the surface during the post annealing process ( Figure 2 a). Alternatively, an immersion of the 3D perovskite film in the IPA solution containing the organic salt for 2D can be adopted, instead of dripping the solution, in order to induce the 2D capping layer ( Figure 2 b) [ 25 ].…”

“…An IPA solution containing BAI and formamidinium iodide (FAI) with different ratios was employed in an attempt to form the capping layer on top of the 3D perovskite with excess PbI 2 , resulting in the highest photovoltaic performance when the same molar ratio between BAI and FAI was employed (BAI:FAI = 1:1) to form a quasi-2D layer—(BA) 2 (FA) n−1 Pb n I 3n+1 —as confirmed by x-ray diffraction (XRD) [ 39 ]. Similarly, penylethylammonium (PEA) was blended with FA at the same molar ratio, which led to a capping layer composed of a double phase comprised of (PEA) 2 PbI 4 and (PEA) 2 (FA)Pb 2 I 7 [ 33 ].…”

Self‐Additive Low‐Dimensional Ruddlesden–Popper Perovskite by the Incorporation of Glycine Hydrochloride for High‐Performance and Stable Solar Cells

“…Recently, more and more research is going into efforts to improve the photovoltaic performances of low dimensional RP perovskites, including: the in situ growth of high‐quality RP perovskite materials, [ 28 ] the preparation of 2D passivation layer, [ 29 ] the modification of quasi‐2D perovskite/hole‐transporting layer interface, [ 30 ] and the dimension regulation of 2D/3D heterojunction perovskite. [ 31 ] Whereas, most of the researchers focused on the design on the new type of low dimensional RP perovskite materials.…”