B. Organic/Inorganic Hybrid Perovskites
Organic-inorganic hybrid perovskites (OIHPs) have generated broad interest in recent years because of their potential for use in optoelectronic devices (e.g., solar cells, light emitting diodes, and detectors). On the other hand, OIHP quantum wells initially drew attention because of their extraordinary electronic structures. Photoexcited electron-hole pairs, termed excitons, are quantum-confined in these systems because the thicknesses of the 2D quantum wells are smaller than the sizes of the excitons. As in other quantum-confined systems, the optical band gaps in 2D OIHPs can be tuned with control over the thicknesses of the quantum wells. These 2D OIHPs have been exploited to enable solar cells with much improved stability compared with 3D OIHPs based ones, and light-emitting devices with high efficiencies.
1. Functional Organic Cations
In earlier works, the organic layers between lead-halide quantum wells primarily acted as insulating dielectrics. The Coulombic couplings that drive energy transfer between neighboring quantum wells, which are separated by approximately 0.7 nm, are relatively weak (less than kBT at ambient conditions). For this reason, we recently developed layered 2D perovskites with functional organic cations whose electronic states more readily mix with those of the quantum wells, thereby promoting transport of electrons between quantum wells. We are actively investigating how these functional organic cations would change the optoelectronic properties of these materials, aiming to achieve hybrid materials with novel properties, and disclose rigorous structure-property correlations to guide further design.
Selected Publications:
2. Chiral OIHPs
Chirality, a fundamental concept for matters that cannot be super-imposed with their mirror images, is ubiquitous in almost all branches of natural science. One interesting example to functionalize low dimensional OIHPs is to incorporate chiral organic spacer cations to impart chirality to such perovskites (chiral OIHPs). These chiral OIHPs combine the good crystallinity and excitonic nature of 2D OIHPs with chiral functionality, enabling chiral-optoelectronic and chiral-spintronic properties. For example, chiral OIHPs have been used in emission and detection of polarized light, spin-selective transport, and ferroelectrics. Further, the chiral phonons were recently proposed to generate spin currents in a chiral 2D-OIHPs when subjected to a thermal gradient, which indicates the potential of chiral 2D-OIHPs for spin caloritronic applications. We are particularly interested in design chiral organic molecules (cations) that can be incorporated into 2D OIHPs for new properties and applications.
Selected Publications:
-
J. Am. Chem. Soc. 2021, 143, 18114–18120. Link
