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Heavy Water Additive in Formamidinium: A Novel Approach to Enhance Perovskite Solar Cell Efficiency
Author(s) -
Solanki Ankur,
Tavakoli Mohammad Mahdi,
Xu Qiang,
Dintakurti Sai S. H.,
Lim Swee Sien,
Bagui Anirban,
Hanna John V.,
Kong Jing,
Sum Tze Chien
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201907864
Subject(s) - formamidinium , deuterium , materials science , perovskite (structure) , spectroscopy , kinetic isotope effect , density functional theory , perovskite solar cell , passivation , fourier transform infrared spectroscopy , chemical physics , energy conversion efficiency , analytical chemistry (journal) , nanotechnology , chemistry , atomic physics , crystallography , chemical engineering , computational chemistry , optoelectronics , physics , organic chemistry , quantum mechanics , layer (electronics) , engineering
Heavy water or deuterium oxide (D 2 O) comprises deuterium, a hydrogen isotope twice the mass of hydrogen. Contrary to the disadvantages of deuterated perovskites, such as shorter recombination lifetimes and lower/invariant efficiencies, the serendipitous effect of D 2 O as a beneficial solvent additive for enhancing the power conversion efficiency (PCE) of triple‐A cation (cesium (Cs)/methylammonium (MA)/formaminidium (FA)) perovskite solar cells from ≈19.2% (reference) to 20.8% (using 1 vol% D 2 O) with higher stability is reported. Ultrafast optical spectroscopy confirms passivation of trap states, increased carrier recombination lifetimes, and enhanced charge carrier diffusion lengths in the deuterated samples. Fourier transform infrared spectroscopy and solid‐state NMR spectroscopy validate the N–H 2 group as the preferential isotope exchange site. Furthermore, the NMR results reveal the induced alteration of the FA to MA ratio due to deuteration causes a widespread alteration to several dynamic processes that influence the photophysical properties. First‐principles density functional theory calculations reveal a decrease in PbI 6 phonon frequencies in the deuterated perovskite lattice. This stabilizes the PbI 6 structures and weakens the electron–LO phonon (Fröhlich) coupling, yielding higher electron mobility. Importantly, these findings demonstrate that selective isotope exchange potentially opens new opportunities for tuning perovskite optoelectronic properties.