Researchers from the University of Twente, Academy of Sciences of the Czech Republic, AMOLF, Universidad Andres Bello and University of Oxford have developed a way to create highly ordered semiconductor material at room temperature, that could make optoelectronics more efficient by controlling the crystal structure and reducing the number of defects at the nanoscale.
The team focused on metal halide perovskites. Making these materials with one single orientation (or in other words with highly ordered grains) has been a challenge and thus far, they have mainly been used in the non-ordered polycrystalline form. This can limit their use in applications such as LEDs, where high order and low density of defects are needed. Normally, these highly ordered semiconductors require high processing temperatures. But in this new process, the researchers skip the heat and build up the material layer by layer using a pulsed laser.
The scientists demonstrated the epitaxial growth of cubic (α)-CH3NH3PbI3 films on lattice-matched KCl substrates by pulsed laser deposition at room temperature. Epitaxial stabilization of α-CH3NH3PbI3 was confirmed via reciprocal space mapping, X-ray diffraction pole figures, electron backscatter diffraction and photoluminescence.
A bandgap of 1.66 eV stable for over 300 days and Urbach energies of 12.3 meV for 15-nm-thick films were demonstrated.
The impact of strain on α-phase stabilization was corroborated by first-principles density functional theory calculations, which also predicted substantial bandgap tunability.
This work demonstrates the potential of pulsed laser deposition for vapor-phase heteroepitaxial growth of metal halide perovskites, inspiring studies to unlock novel functionalities.
