A single crystal of a lead−iodine-based 2D perovskite having naphthalene diimide ammonium (NDIA) molecules as organic layers was developed, and the charge transport property was studied using field-effect transistors (FETs) measurements. Structure determination reveals the layered alternative stacking of lead iodide sheets and NDIA bilayers. The presence of NDIA promoted the lead iodide octahedron to form the unique three-point co-planar [Pb 3 I 10 ] 4− unit, which then connected into the 2D network in a corner-sharing manner. The NDIA cations closely stacked into 1D chains within the bilayers that were being sandwiched between the inorganic layers. FET characteristics of the single crystal obtained at room temperature demonstrate V DS -dependent electron and hole transport behavior with mobilities reaching up to more than 5 × 10 −3 cm 2 V −1 s −1 . The 1D stack of NDIAs contributes greatly to the performance improvement for both the charge transport and the stability.
Excitons
have fundamental impacts on optoelectronic properties
of semiconductors. Halide perovskites, with long carrier lifetimes
and ionic crystal structures, may support highly mobile excitons because
the dipolar nature of excitons suppresses phonon scattering. Inspired
by recent experimental progress, we perform device modeling to rigorously
analyze exciton formation and transport in methylammonium lead triiodide
under local photoexcitation by using a finite element method. Mobile
excitons, coexisting with free carriers, can dominate photocurrent
generation at low temperatures. The simulation results are in excellent
agreement with the experimentally observed strong temperature and
gate dependence of carrier diffusion. This work signifies that efficient
exciton transport can substantially influence charge transport in
the family of perovskite materials.
1D organic metal halide hybrids (OMHHs) exhibit strongly anisotropic optical properties, highly efficient light emission, and large Stokes shift, holding promise for novel photodetection and lighting applications. However, the fundamental mechanisms governing their unique optical properties and in particular the impacts of surface effects are not understood. Herein, 1D C4N2H14PbBr4 by polarization‐dependent time‐averaged and time‐resolved photoluminescence (TRPL) spectroscopy, as a function of photoexcitation energy, is investigated. Surprisingly, it is found that the emission under photoexcitation polarized parallel to the 1D metal halide chains can be either stronger or weaker than that under perpendicular polarization, depending on the excitation energy. The excitation‐energy‐dependent anisotropic emission is attributed to fast surface recombination, supported by first‐principles calculations of optical absorption in this material. The fast surface recombination is directly confirmed by TRPL measurements, when the excitation is polarized parallel to the chains. The comprehensive studies provide a more complete picture for a deeper understanding of the optical anisotropy in 1D OMHHs.
Excitons are often given negative connotation in solar energy harvesting in part due to their presumed short diffusion lengths. We investigate exciton transport in singlecrystal methylammonium lead tribromide (MAPbBr 3 ) microribbons via spectrally, spatially, and temporally resolved photocurrent and photoluminescence measurements. Distinct peaks in the photocurrent spectra unambiguously confirm exciton formation and allow for accurate extraction of the low temperature exciton binding energy (39 meV). Photocurrent decays within a few μm at room temperature, while a gate-tunable long-range photocurrent component appears at lower temperatures (about 100 μm below 140 K). Carrier lifetimes of 1.2 μs or shorter exclude the possibility of the long decay length arising from slow trappedcarrier hopping. Free carrier diffusion is also an unlikely source of the highly nonlocal photocurrent, due to their small fraction at low temperatures. We attribute the long-distance transport to high-mobility excitons, which may open up new opportunities for novel excitonbased photovoltaic applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.