Molecular Design and Operational Stability: Toward Stable 3D/2D Perovskite Interlayers.

Sanghyun Paek,Hoichang Yang,Marius Franckevičius,Abdullah M Asiri,Nikita Drigo,Pascal A Schouwink,Clémence Corminboeuf,Hobeom Kim,Kun‐Han Lin,Hiroyuke Kanda,Mohammad Khaja Nazeeruddin,Kyung Taek Cho,Mingyuan Pei,Cristina Roldán‐Carmona,Hyung Joong Yun,Rokas Gegevičius

doi:10.1002/advs.202001014

Abstract

Despite organic/inorganic lead halide perovskite solar cells becoming one of the most promising next‐generation photovoltaic materials, instability under heat and light soaking remains unsolved. In this work, a highly hydrophobic cation, perfluorobenzylammonium iodide (5FBzAI), is designed and a 2D perovskite with reinforced intermolecular interactions is engineered, providing improved passivation at the interface that reduces charge recombination and enhances cell stability compared with benchmark 2D systems. Motivated by the strong halogen bond interaction, (5FBzAI)2PbI4 used as a capping layer aligns in in‐plane crystal orientation, inducing a reproducible increase of ≈60 mV in the V oc, a twofold improvement compared with its analogous monofluorinated phenylethylammonium iodide (PEAI) recently reported. This endows the system with high power conversion efficiency of 21.65% and extended operational stability after 1100 h of continuous illumination, outlining directions for future work.

Highlights

Cation, perfluorobenzylammonium iodide (5FBzAI), is designed and a 2D perovskite with reinforced intermolecular interactions is engineered, providing improved passivation at the interface that reduces charge
Motivated by the strong halogen bond interaction, (5FBzAI)2PbI4 used as a capping layer aligns in in-plane crystal orientation, inducing a reproducible increase of ≈60 mV in the Voc, a twofold improvement compared with its analogous monofluorinated phenylethylammonium iodide (PEAI)
We have investigated a monofluorinated PEAI cation (FPEAI) recently reported in the literature,[14,22] compared with a novel pentafluorobenzyl ammonium (5FBzAI) cation, which contains a methylene bridge that confers increased rigidity, and compensates the strong dispersion forces induced by the five fluorine units

Summary

Introduction

Cation, perfluorobenzylammonium iodide (5FBzAI), is designed and a 2D perovskite with reinforced intermolecular interactions is engineered, providing improved passivation at the interface that reduces charge. Because the activation energy for defect diffusion is lower at the interface than in the bulk, and in the 2D it preferably occurs within the inorganic [PbI6]−4 planes, a 3D/2D bilayer containing irregularly grown FPEA2PbI4 crystals will be more prone to ion migration.[32] Given the strong correlation between ion migration and degradation,[18] such a different orientation will certainly impact the 3D/2D optoelectronic behavior in long-term, as later demonstrated in this manuscript.

Results

Conclusion