Universal Bifacial Stamping Approach Enabling Reverse‐Graded Ruddlesden‐Popper 2D Perovskite Solar Cells. Issue 29 (24th June 2022)

• Record Type: Journal Article
• Authors: Lee, Junwoo; Jang, Gyumin; Ma, Sunihl; Lee, Chan Uk; Son, Jaehyun; Jeong, Wooyong; Moon, Jooho
• Is Part Of: Small. Volume 18:Issue 29(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-24
• Subjects: bifacial stamping -- highly oriented crystals -- retarded crystallization -- reverse‐graded structure -- Ruddlesden‐Popper perovskites; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.202202159
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: Quasi 2D perovskite solar cells (PSCs) are promising light absorbers that overcome the inherent instabilities of 3D perovskites. High‐performance and stable 2D PSCs require careful control over the crystallographic orientation and phase distribution. This study introduces a simple and universal bifacial stamping method to obtain highly oriented perovskite crystals with a reverse‐graded structure, where the low‐ n ‐value 2D perovskite phases are located mainly at the film surfaces. Bifacial stamping of 3D perovskite films atop the 2D films enables incorporation of 2D spacer cations into the 3D film surfaces, forming reverse‐graded quasi‐2D perovskite films. During stamping, suppressed evaporation of the precursor solvent induces heterogeneous nucleation from the contact interface between the 2D and 3D films, resulting in well‐crystallized perovskite films having out‐of‐plane alignments with respect to the substrate. Thus, a highly oriented and reverse‐graded quasi‐2D perovskite with an average n value of 18 is obtained with power conversion efficiency exceeding 17% and high open‐circuit voltage of 1.11 V for iso ‐butylammonium ( iso ‐BA)‐based ( iso ‐BA2 MA n −1 Pb n I3 n +1 ) PSCs. The unencapsulated device retains 92% of its initial efficiency after aging at 40 ± 5% relative humidity for 1200 h. This work provides a new strategy for fabricating highly oriented and phase‐controlled quasi‐2D PSCs. Abstract : Highly oriented quasi‐2D perovskite with reverse‐graded structure is obtained by bifacial stamping. The bulky cations are transferred from the 2D supply to 3D perovskite substrates during stamping, inducing transformation into quasi‐2D perovskite. The solvent evaporation inhibited by stamping retards crystallization, resulting in the vertical alignment of the quasi‐2D perovskite with reverse‐graded structure.