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Origin of Open‐Circuit Voltage Enhancements in Planar Perovskite Solar Cells Induced by Addition of Bulky Organic Cations / Chieh‐Ting Lin, Jinho Lee, Jinhyun Kim, Thomas J. Macdonald, Jonathan Ngiam, Bob Xu, Matyas Daboczi, Weidong Xu, Sebastian Pont, Byoungwook Park, Hongkyu Kang, Ji‐Seon Kim, David J. Payne, Kwanghee Lee, James Durrant, Martyn A. McLachlan

Advanced Functional Materials, Volume: 30, Issue: 7, Start page: 1906763

Swansea University Author: James Durrant

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DOI (Published version): 10.1002/adfm.201906763

Abstract

The origin of performance enhancements in p‐i‐n perovskite solar cells (PSCs) when incorporating low concentrations of the bulky cation 1‐naphthylmethylamine (NMA) are discussed. A 0.25 vol % addition of NMA increases the open circuit voltage (Voc) of methylammonium lead iodide (MAPbI3) PSCs from 1....

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Published in: Advanced Functional Materials
ISSN: 1616-301X 1616-3028
Published: Wiley 2020
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URI: https://cronfa.swan.ac.uk/Record/cronfa53130
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Abstract: The origin of performance enhancements in p‐i‐n perovskite solar cells (PSCs) when incorporating low concentrations of the bulky cation 1‐naphthylmethylamine (NMA) are discussed. A 0.25 vol % addition of NMA increases the open circuit voltage (Voc) of methylammonium lead iodide (MAPbI3) PSCs from 1.06 to 1.16 V and their power conversion efficiency (PCE) from 18.7% to 20.1%. X‐ray photoelectron spectroscopy and low energy ion scattering data show NMA is located at grain surfaces, not the bulk. Scanning electron microscopy shows combining NMA addition with solvent assisted annealing creates large grains that span the active layer. Steady state and transient photoluminescence data show NMA suppresses non‐radiative recombination resulting from charge trapping, consistent with passivation of grain surfaces. Increasing the NMA concentration reduces device short‐circuit current density and PCE, also suppressing photoluminescence quenching at charge transport layers. Both Voc and PCE enhancements are observed when bulky cations (phenyl(ethyl/methyl)ammonium) are incorporated, but not smaller cations (Cs/MA)—indicating size is a key parameter. Finally, it demonstrates that NMA also enhances mixed iodide/bromide wide bandgap PSCs (Voc of 1.22 V with a 1.68 eV bandgap). The results demonstrate a facile approach to maximizing Voc and provide insights into morphological control and charge carrier dynamics induced by bulky cations in PSCs.
Issue: 7
Start Page: 1906763