Defect Passivation by Amide-Based Hole-Transporting Interfacial Layer Enhanced Perovskite Grain Growth for Efficient p–i–n Perovskite Solar Cells

Abstract

In this study, we synthesized four acceptor–donor–acceptor type hole-transporting materials (HTMs) of SY1–SY4 for an HTMs/interfacial layer with carbazole as the core moiety and ester/amide as the acceptor unit. These HTMs contain 4-hexyloxyphenyl substituents on the carbazole N atom, with extended π-conjugation achieved through phenylene and thiophene units at the 3,6-positions of the carbazole. When using amide-based HTMs SY2 as a dopant-free HTM in a p–i–n perovskite solar cell (PSC), we achieved a power conversion efficiency (PCE) of 13.59% under AM 1.5G conditions (100 mW cm–2); this PCE was comparable with that obtained when using PEDOT:PSS as the HTM (12.33%). Amide-based SY2 and SY4 HTMs showed a larger perovskite grain than SY1 and SY3 because of the passivation of traps/defects at the grain boundaries and stronger interaction with the perovskite layer. In further investigation, we demonstrated highly efficient and stable PSCs when using the dopant-free p–i–n device structure indium tin oxide/NiO x /interfacial layer (SY-HTMs)/perovskite/PC61BM/BCP/Ag. The interfacial layer improved the PCEs and large grain size (micrometer scale) of the perovskite layer because of defect passivation and interface modification; the amide group exhibited a Lewis base adduct property coordinated to Ni and Pb ions in NiO x and perovskite, bifacial defect passivation and reduced the grain boundaries to improve the crystallinity of the perovskite. The amide-based SY2 exhibited the stronger interaction with the perovskite layer than that of ester-based SY1, which is related to the observations in X-ray absorption near edge structure (XANES). The best performance of the NiO x /SY2 device was characterized by a short-circuit current density (J sc) of 21.76 mA cm–2, an open-circuit voltage (V oc) of 1.102 V, and a fill factor of 79.1%, corresponding to an overall PCE of 18.96%. The stability test of the PCE of the NiO x /SY2 PSC device PCE showed a decay of only 5.01% after 168 h; it retained 92.01% of its original PCE after 1000 h in Ar atmosphere. Time-resolved photoluminescence spectra of the perovskite films suggested that the hole extraction capabilities of the NiO x /SY-HTMs were better than that of the bare NiO x . The superior film morphologies of the NiO x /SY-HTMs were responsible for the performances of their devices being comparable with those of bare NiO x -based PSCs. The photophysical properties of the HTMs were analyzed through time-dependent density functional theory with the B3LYP functional.

Designing New Indene-Fullerene Derivatives as Electron-Transporting Materials for Flexible Perovskite Solar Cells

“…Upon the formation of the perovskite/ICMA contact, electron-donating moieties in the fullerene derivatives (amine or amide groups) could form a dative bond with uncoordinated Pb 2+ ions. 64 The largest shift has been observed for the NHAc-Me-ICMA , which contains both oxygen and nitrogen donors. The reference PCBM displayed a smaller shift, as the coordinating ability of the oxygen atom in its ester group is weaker.…”

Tetra-indole core as a dual agent: a hole selective layer that passivates defects in perovskite solar cells

“…The depletion layer width (W) was calculated to be 168.51 nm for the pristine PSC, and this increases to 198.55 nm for TTI passivated PSCs To further substantiate the passivation effects, the electrochemical impedance spectroscopic (EIS) analysis was performed (Figure 7f), and the spectral analysis provide insight in the charge transfer and recombination behavior. 57,58 The Nyquist plots was measured in the dark at 0.8V. We deduced that the recombination resistance in the TTI passivated PSC (larger semicircle) is higher as compared to the pristine PSCs, TTI passivation leads to larger recombination resistance and elucidate its role in passivating the defects.…”

A Cost‐Effective D‐A‐D Type Hole‐Transport Material Enabling 20% Efficiency Inverted Perovskite Solar Cells†

“…However, previous D‐A‐D molecular HTMs in inverted PVSCs were often synthesized via multiple steps, preventing their broad applications. [ 16d‐16f,19 ]…”