Transition Metal Perovskite Chalcogenides: Emerging Semiconductors for Visible and Infrared Optoelectronics
Large-scale deployment of electronic, photonic, and energy technologies rely on continuous discovery and invention of high performance electronic materials with earth abundant compositions. Carrier mobility and density of states (DOS) are two critical material parameters in light-matter interaction to enable efficient, high performance light absorption, emission, and detection. While the advantages of high carrier mobility are evident, large density of states can lead to desirable electronic and optical properties such as enhanced light absorption and emission (efficient solar energy conversion and lighting), high carrier density (high current, power density), and large thermopower (thermoelectrics). However, there is an inverse correlation between the two attributes in current semiconductors (Fig. 1a). To this end, transition metal perovskite chalcogenides (TMPCs), an emerging class of materials with d0 configuration, moderately covalent bonding, have been proposed for optoelectronic applications.1-7 TMPCs have a general chemical formula of ABX3, where A is a metal such as Ba, Sr, B is a transition metal such as Ti, Zr, and X is S or Se. High DOS is expected from the combination of highly symmetric perovskite structure and degenerate d orbitals. TMPCs can be viewed as the inorganic alternatives to hybrid halide perovskites, with stable, benign, abundant composition, and ultrahigh absorption coefficients (Fig. 1b).1,5 On the other hand, TMPCs can also be viewed as the chalcogenide counterparts of perovskite oxides, with much lower bandgap and improved responsivity to visible and infrared light (Fig. 1c).1,8 The coexistence of high DOS and mobility opens opportunities for a broad range of photonic, optoelectronic, and energy applications, including solar cells1,5-7,9-11, mid infrared optics12-14, thermoelectrics15,16, light emitting devices5,17 and photoelectrochemical catalysis6.