Surprises in molecular polaritonics and photonics

We will describe 2 unexpected recent observations that may have important applications for electroluminescent devices and integrated photonics using molecular materials. In the first, we will describe experiments on microcavities containing a thin film of zinc phtalocyanine where the photoluminescence quantum yield is enhanced by >500 as compared to the out-of-cavity case. This behavior is vastly different from that of most molecular thin films, where the angular emission and photoluminescence quantum yield enhancements can be easily described using classical dipole emission within inhomogeneous dielectric environments (i.e. Purcell effect). We will discuss the origins of this effect and the role of long-lived triplet and excimer states. In the second part of the talk, we will show that contrary to the naïve assumption that amorphous organic thin films are centrosymmetric, long-range order is present in most films composed of molecules possessing a permanent dipole moment as manifested by the giant surface potential that can be measured on many such films. This phenomenon has received much attention in the context of its impact on OLED performance and has been coined spontaneous orientation polarization. However, a natural consequence of this that has not yet been appreciated is the opportunity it offers in the context of second-order nonlinear optics. By using molecules with a large permanent dipole moment combined with a large hyperpolarizability, we can engineer films with high second-order susceptibiltiies for applications in electro-optics and nonlinear photonics. We will demonstrate this for several materials and show how such films can be integrated into novel photonic devices.