Abstract
Perovskite solar cells (PSCs) suffer from deep level defects which would cause charge accumulation and consequent non-radiative recombination losses during the operation of the device, limiting their power conversion efficiencies (PCEs). Herein, we employ small molecule dicyandiamide (DICY) as a passivating agent for the deep level defects of perovskite thin films. The C-N bond (C-NH-C) of DICY is found to be Lewis acidic due to the inductive effect of Lewis basic imine (-C ≡ N) and cyano (-C ≡ N) functional groups of DICY. So, the synergistic effect of the functional groups in DICY could passivate the deep level defects by forming a Lewis adduct by coordination bonds, which is proved by density functional theory calculations and SCLC measurements. The elimination of the deep level defects of perovskite thin films results in a reduced charge recombination and more efficient charge transport. Consequently, the optimized PSC based on DICY shows a champion PCE of 20.05%. Our findings reveal the mechanisms of the synergistic effect of the functional groups in the small molecule on passivating the deep level defects of perovskites.
Original language | English |
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Pages (from-to) | 5922-5928 |
Number of pages | 7 |
Journal | Journal of Materials Chemistry C |
Volume | 10 |
Issue number | 15 |
DOIs | |
State | Published - 8 Mar 2022 |