Professor Stephen Forrest and his group focus primarily on the investigation of materials used in optoelectronic device applications. These materials fall into two categories: group 3-5 semi-conductors such as InP and GaAs and related compounds for use in photonics, and organic semiconductors used in displays, photovoltaic cells, and thin film transistors.

New materials and their growth properties have long been a subject of interest in our group.
For example, we demonstrated that InGaAsN grown by gas source molecular beam epitaxy
(a capability that is available to the group using a Riber gas source MBE system) is a material of considerable interest in the short to midwavelength infrared spectral range for use in detection and laser light generation. Both such devices have been demonstrated in this materials system. In addition, we have a long standing activity in using InGaAs lattice matched to InP for ultrahigh sensitivity IR detection applications in fiber optic communications and focal plane array imaging. Among the “firsts” by our group is the demonstration of planar InGaAs pin and avalanche photodetectors which are now the standard used in all long haul fiber optic communication systems. We have also had a significant and long term effort in integrating multiple photonic devices onto a single chip. A particular area of interest has been to generate a simple platform technology for realizing photonic integrated circuits (PICs) consisting of any desired combination of lasers, semiconductor optical amplifiers, photodetectors, waveguides, modulators, et cetera. We have engineered a highly flexible and low cost technology that avoids complicated semiconductor regrowth processes, called asymmetric twin waveguide (ATG) technology. Currently, ATG-based devices are finding their way into numerous applications such as 10Gb/s Ethernet transmitters and receivers. More recent work in these material systems has focused on exploring quantum dot intermediate band photovoltaic cells for very high solar conversion efficiency applications.

Organic semiconductors have been the subject of intense worldwide interest for at least 50 years, but only recently have they been recognized as offering practical solutions to a new generation of displays, electronics, efficient light sources, and solar energy conversion devices. Organic semi-conductors, which are primarily carbon-rich synthetic compounds, are typically used as dyes in clothing, paints, and in photographic prints. However, in the mid 1980’s they were shown to provide low voltage electroluminescence when placed in a thin film bilayer structure. These structures, called organic light emitting devices (OLEDs), are currently finding commercial applications as bright, flexible and efficient display elements and white light sources. Our work has focused on a demonstrating a new process called “electrophosphorescence” whereby a heavy metal atom such as Ir or Pt is attached to the organic “ligand” group induces fast and efficient luminescence from both the quantum mechanical singlet and triplet states, leading to 100% internal quantum efficiency. These OLEDs currently represent the most efficient electro-luminescent devices available for either displays or white light sources used to replace incandescent lighting, and eventually fluorescent lighting. Similar materials can also be used in “double heterojunction” thin film organic solar cells. The ability to deposit these cells on plastic films gives them potential as an effective solar energy conversion device that may eventually replace silicon with a lower cost, lighter weight alternative. Our work in these cells is directed at finding materials and architectures leading to very high solar energy conversion efficiencies.

Professor Forrest is a member of the American Physical Society, a Fellow of IEEE, and the Optical Society of America.

Management of Singlet and Triplet Excitons for Efficient White Organic Light Emitting Devices, (Y. Sun, N. Giebink, H. Kanno, B. Ma, M.E. Thompson, and S.R. Forrest), Nature 440, 908 (2006).

White Stacked Electrophosphorescent Organic Light-emitting Devices Employing MoO₃ as a Charge Generation Layer, (H. Kanno, R.J. Holmes, Y. Sun and S.R. Forrest), Adv. Mat. 18, 339 (2006).

Photonic Integration Using Asymmetric Twin-Waveguide (ATG) Technology. I. Concepts and Theory, (F. Xia, V.M. Menon, and S.R. Forrest), IEEE J. Sel. Topics in Quant. Electron. 11, 17 (2005).

Controlled Growth of a Molecular Bulk Heterojunction Photovoltaic Cell, (F. Yang, M. Shtein, and S.R. Forrest), Nat. Mater. 4, 39 (2004).

Strong Exciton-Photon Coupling and Exciton Hybridization in a Thermally Evaporated Polycrystalline Film of an Organic Small Molecule, (R.J. Holmes and S.R. Forrest), Phys. Rev. Lett. 93, 186404 (2004).

Organic Small Molecule Solar Cells with a Homogeneously Mixed Copper Phthalocyanine: C₆₀ Active Layer, (S. Uchida, J. Xue, B.P. Rand and S.R. Forrest), Appl. Phys. Lett 84, 4218 (2004).

The Path to Ubiquitous and Low Cost Organic Electronic Appliances on Plastic, (S.R. Forrest), Nature (London), invited, 428, 911 (2004).

Control of Quality Factor and Critical Coupling in Microring Resonators Through Integration of a Semiconductor Optical Amplifier, (V.M. Menon, W. Tong, and S.R. Forrest), IEEE Photon. Technol. Lett. 16, 1343 (2004).

High Efficiency Phosphorescent Emission From Organic Electroluminescent Devices, (M.A. Baldo, D.F. O'Brien, Y. You, A. Shoustikov, M.E. Thompson and S.R. Forrest), Nature 395, 151 (1998).

Ultrathin Organic Films Grown by Organic Molecular Beam Deposition and Related Techniques, (S.R. Forrest), Chem. Rev. 97, 1793 (1997).