Abstract
The chemical nature of the organic cations governs the optoelectronic properties of two-dimensional organic-inorganic perovskites. But its mechanism is not fully understood. Here, we apply femtosecond broadband sum frequency generation vibrational spectroscopy to investigate the molecular conformation of spacer organic cations in two-dimensional organic-inorganic perovskite films and establish a correlation among the conformation of the organic cations, the charge carrier mobility, and broadband emission. Our study indicates that both the mobility and broadband emission show strong dependence on the molecular conformational order of organic cations. The gauche defect and local chain distortion of organic cations are the structural origin of the in-plane mobility reduction and broad emission in two-dimensional organic-inorganic perovskites. Both of the interlayer distance and the conformational order of the organic cations affect the out-of-plane mobility. This work provides molecular-level understanding of the conformation of organic cations in optimizing the optoelectronic properties of two-dimensional organic-inorganic perovskites.
Highlights
The chemical nature of the organic cations governs the optoelectronic properties of twodimensional organic-inorganic perovskites
Some studies suggest that increasing the length of organic cations can cause structural reorganization, leading to the formation of 1D quantum confinement effect[17,20], while others claim that the charge transport property of 2D organic–inorganic hybrid perovskites (OIHPs) films can be efficiently improved by reducing the interlayer distance and further giving rise to better device performance[18]
Trapped charges or neutral Coulomb-bound electron–hole pairs will not be detected[31]. This technique has been demonstrated to be a powerful tool for determining the effective charge-carrier mobility along the film plane[12,32,33,34,35,36,37]
Summary
The chemical nature of the organic cations governs the optoelectronic properties of twodimensional organic-inorganic perovskites. Important milestones have been achieved through this chemical engineering[9], how the chemical nature of the organic cations within the inorganic framework governs the structural and optoelectronic properties of 2D OIHPs is not fully understood While such performance is strongly determined by the charge-carrier mobility (μ), the excited carrier lifetime (τ), and emission characteristics[15,16], several views on how the structural parameters of spacer cations affect the chargecarrier mobility and PL emission have been proposed[11,17,18,19]. A remarkable dependence of carrier mobility and broad PL emission on the conformational order of the alkyl chains in organic cations is revealed Such finding is achieved thanks to the application of sum frequency generation vibrational spectroscopy (SFG-VS), supplemented by optical-pump terahertz-probe spectroscopy (OPTPS), currentvoltage (I–V) measurements, temperature-dependent PL spectroscopy, and X-ray diffraction (XRD) measurements. This study highlights the importance of molecular-level structural engineering in hybrid perovskites to control the optoelectronic properties
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
