In situ CsPbBr3 architecture engineered in electrospun fibers and its ultrafast charge-transfer dynamics

Abstract

All-inorganic lead halide perovskite nanocrystals (NCs) have witnessed a rapid progression in the field of optoelectronics as well as photovoltaic applications. However, their environmental instability, tedious synthesis protocols, and post treatments hinder their further development for energy-harvesting devices. However, the aforementioned obstacles can be easily tackled by engineering them with a piezoelectric polymer, in situ perovskite construction, and by encapsulation. To date, the fundamental photophysical study of piezoelectric polymers with perovskite materials is still in early phase, and deeper understanding could illustrate a road map for their further advancement in solar cells and photodetectors, which is the main focus of this study. Herein, we present a facile route for the synthesis of highly stable cesium lead bromide (CsPbBr₃) inside poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) fibers using a single step in situ electrospinning technique. X-Ray diffraction analysis depicted the successful formation of the β-phase in PVDF-HFP along with CsPbBr₃ during the electrospinning process. High-resolution transmission electron microscopy (HR-TEM) images clearly evidenced the arrangement of CsPbBr₃ inside the fiber matrix. Moreover, the synthesized CsPbBr₃@PVDF-HFP fibers exhibited narrow light emission, which supported the optical and structural analysis. To understand the charge-transfer process in the CsPbBr₃@PVDF-HFP fibers, transient absorption (TA) spectroscopy was employed. Different pump excitations were employed to identify the carrier-relaxation mechanism in the type-I CsPbBr₃@PVDF-HFP fiber architecture. TA spectroscopy studies clearly suggested the transfer of charge carriers from CsPbBr₃ to PVDF-HFP upon 300 nm pump excitation, which was a thermodynamically viable process. Our results provide a facile and effective strategy for the preparation of a stable perovskite architecture and an in depth study of the photophysical properties, which could provide significant assistance in the development of highly efficient perovskite-based solar cell and photodetector applications.