  New blends of simply synthesized quasi two-dimensional (quasi-2D) hydrophobic
perovskite semiconductors, employed in high performance light emitting diodes
(LEDs) which function due to excitonic energy transfer effects, are reported.
These materials are self-assembled blends of 2D, quasi-2D and three-dimensional
(3D) hybrid organic-inorganic semiconductors (HOIS). Moreover, shown for the
first time, crude mixing of 3D perovskite and unprotonated amines provides
similar semiconductors. HOIS reported here are based on the organic cations
CH3NH3+, CH3(CH2)7CH=CH(CH2)8NH3+ or C6H5CH2CH2NH3+ and inorganic networks
formed out of PbX42- anions (X=I, Br, Cl). HOIS exhibit strong bound excitonic
states with increased oscillator strength at room temperature, tunable via
simple halide substitution. HOIS blends manifest energy transfer effects, where
adjacent nanoparticles of different band gap energies (Eg) transfer optical
energy to those with the lowest Eg; the suggested light emission mechanism
here. LED fabrication is attained via a single deposition of the hydrophobic
mixture, reducing device complexity, cost and degradability. LED's diodic
behavior is observed even under light albeit its photovoltaic and
photoconductive quasi-2D and 3D components. LED devices exposed for over than
four months under adverse laboratory conditions, showed stable light emission.
Further research on this class of quasi-2D/3D HOIS mixtures is expected to lead
to novel quantum electronic devices.
