Tunable exciton binding energy in 2D hybrid layered perovskites through donor-acceptor interactions within the organic layer

The strength of electrostatic interactions within semiconductors strongly affects their performance in optoelectronic devices. An important target is the tuning of a material's exciton binding energy-the energy binding an electron-hole pair through the electrostatic Coulomb force-independent of its electronic band gap. Here, we report on the doping of a family of two-dimensional hybrid perovskites, in which inorganic lead halide sheets alternate with naphthalene-based organic layers, with tetrachloro-1,2-benzoquinone (TCBQ). For four out of sevenn = 1 perovskites, the incorporation of the electron-accepting TCBQ dopant into the organic sublattice containing the electron-donating naphthalene species enabled the tuning of the materials' 1sexciton binding energy. The naphthalene-TCBQ electron donor-acceptor interactions increased the electrostatic screening of the exciton, in turn lowering its binding energy relative to the undoped perovskite-by almost 50% in one system. Structural and optical characterization showed that the inorganic lattice is not significantly perturbed even though the layer-to-layer spacing increases upon molecular dopant incorporation. The strength of electrostatic interactions in semiconductors strongly affects their performance in optoelectronic devices. Now, doping two-dimensional naphthalene-based lead halide perovskites with tetrachloro-1,2-benzoquinone has been shown to introduce donor-acceptor interactions within the organic network, without disrupting the inorganic sublattice. This in turn altered the energy of the materials' electron-hole electrostatic Coulomb interactions.