Conformational Order of Alkyl Side Chain of Poly(3-alkylthiophene) Promotes Hole-Extraction Ability in Perovskite/Poly(3-alkylthiophene) Heterojunction

Abstract

Molecular structures of hole transport materials (HTMs) have significant impact on the optoelectronic properties of perovskite/HTM heterojunction. But the structure–property relationship in the heterojunction remains poorly understood. By using poly­(3-alkylthiophene) (P3AT) as the HTM model, here we apply sum frequency generation vibrational spectroscopy to establish correlations among conformations of P3ATs, the hole extraction ability of P3ATs from the perovskite layer, and the charge mobility of P3ATs. It is revealed that with similar energy-level alignment, the conformational order of alkyl side chains in regioregular P3ATs can effectively regulate the hole extraction ability of P3ATs from perovskite layer by tuning reorganization energy. By contrast, the charge mobility of P3ATs strongly depends on the P3AT backbone’s coplanarity. Our findings decouple the roles of the long-hidden conformational order of alkyl side chain and the polythiophene backbone’s coplanarity on the performance of perovskite/HTM heterojunction, offering useful guidelines for boosting the performance of optoelectronic devices.

Resonant Molecular Modification for Energy Level Alignment in Perovskite Solar Cells

“…We evaluated the hole mobility of BED using the dark J – V curves of a hole-only device (Figure e). The charge mobilities are extracted using the Mott–Gurney equation: μ = 8 J D L 3 /9ε 0 ε r V 2 . According to the cross-sectional SEM analysis (Figure S10), the thickness of the BED/spiro-OMeTAD is determined to be 213.9 nm (spiro-OMeTAD: 195.4 nm).…”

“…47 We evaluated the hole mobility of BED using the dark J−V curves of a hole-only device (Figure 4e). The charge mobilities are extracted using the Mott−Gurney equation: 48…”

Boosting Charge Transport in a 2D/3D Perovskite Heterostructure by Selecting an Ordered 2D Perovskite as the Passivator

“…[20,30] SFG-VS has been shown to be a unique and powerful tool for elucidating the molecular ordering and orientation of the organic cations of OIHPs, [20,31] and hole transport materials of perovskite devices. [18,32] Because the strong interlayer interaction between electron-deficient F atoms and their adjacent phenyl rings aligns the 2D perovskite crystal structure, [33] the orientation of the 2D perovskite layers can be correlated to the orientation of organic cations. [31b] Figure 3a shows the ssp SFG spectra of the phenyl groups of the organic cations.…”

“…SFG‐VS is a second‐order nonlinear coherent optical technique that permits determining the orientational information of a noncentrosymmetric chemical group [20, 30] . SFG‐VS has been shown to be a unique and powerful tool for elucidating the molecular ordering and orientation of the organic cations of OIHPs, [20, 31] and hole transport materials of perovskite devices [18, 32] . Because the strong interlayer interaction between electron‐deficient F atoms and their adjacent phenyl rings aligns the 2D perovskite crystal structure, [33] the orientation of the 2D perovskite layers can be correlated to the orientation of organic cations [31b] .…”

Efficient Light‐Emitting Diodes via Hydrogen Bonding Induced Phase Modulation in Quasi‐2D Perovskites

“…The decay curves were fitted using a biexponential function, and detailed fitting parameters were summarized in Table S1. [ 38 ] The EA‐treated film exhibited the longest average lifetime (τ avg = 11.26 ns) among these films. The inferior suppression of the low‐ n phases ( n ≤ 2) exerted by other anti‐solvent results in a shortened lifetime because of their large exciton binding energy.…”