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Origin of Open‐Circuit Voltage Enhancements in Planar Perovskite Solar Cells Induced by Addition of Bulky Organic Cations
Author(s) -
Lin ChiehTing,
Lee Jinho,
Kim Jinhyun,
Macdonald Thomas J.,
Ngiam Jonathan,
Xu Bob,
Daboczi Matyas,
Xu Weidong,
Pont Sebastian,
Park Byoungwook,
Kang Hongkyu,
Kim JiSeon,
Payne David J.,
Lee Kwanghee,
Durrant James R.,
McLachlan Martyn A.
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201906763
Subject(s) - materials science , perovskite (structure) , photoluminescence , open circuit voltage , band gap , iodide , energy conversion efficiency , passivation , analytical chemistry (journal) , perovskite solar cell , bromide , grain boundary , optoelectronics , chemical engineering , nanotechnology , inorganic chemistry , layer (electronics) , organic chemistry , voltage , chemistry , physics , quantum mechanics , engineering , microstructure , metallurgy
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 ( V oc ) of methylammonium lead iodide (MAPbI 3 ) 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 V oc 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 ( V oc of 1.22 V with a 1.68 eV bandgap). The results demonstrate a facile approach to maximizing V oc and provide insights into morphological control and charge carrier dynamics induced by bulky cations in PSCs.