Photoluminescence of the inorganic-organic layered semiconductor(C6H5C2H4

By mean of subpicosecond pulsed excitation of excitons, we have measured the photoluminescence spectra of ${({\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{C}}_{2}{\mathrm{H}}_{4}\mathrm{N}{\mathrm{H}}_{3})}_{2}\mathrm{Pb}{\mathrm{I}}_{4}$ under a high-excitation regime up to $4\ifmmode\times\else\texttimes\fi{}{10}^{14}\phantom{\rule{0.3em}{0ex}}\text{photons}∕{\mathrm{cm}}^{2}$. At $10\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, two additional lines are observed below the exciton energy by 55 and $75\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ for excitation greater than $2\ifmmode\times\else\texttimes\fi{}{10}^{13}\phantom{\rule{0.3em}{0ex}}\text{photons}∕{\mathrm{cm}}^{2}$. The former is assigned to the amplified spontaneous emission of the excitonic molecule. The latter is presumed to be the emission of a triexciton leaving two excitons behind, because the intensity is proportional to the 2.6 power of the excitation intensity. An elementary model of the triexciton is presented. The dissociation energy of a triexciton is estimated to be $14\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ from the temperature dependence.