The principles and tools of physical and materials chemistry are critical to the energy generation and storage problem. Research in the Ginger Lab focuses on the physical chemistry of nanostructured materials with potential applications in low cost photovoltaics (solar cells), energy efficient light-emitting diodes, and novel biosensors. In particular, we study conjugated polymers, semiconductor nanocrystal quantum dots, and plasmon resonant metal nanoparticles. We develop and apply new combinations of scanning probe microscopy and optical spectroscopy (such as time-resolved EFM, and photoconductive AFM) to understand the basic science behind these materials and their applications in devices. We assemble these materials into new structures using Dip-Pen Nanolithography and bio-inspired materials approaches. In general we are interested in the interplay between the organizational structure, the electrical properties, and the optical properties of nanoscale materials, especially as applied to problems of solar energy. Prospective students should contact David Ginger directly.
Solar Energy: Scanning Probe Microscopy and Nanostructured Photovoltaics
Many promising materials -- such as hybrid perovskites, conjugated polymers, and colloidal quantum dots -- that are being explored for next-generation energy generation and storage exhibit complex structure-function relationships at the nanoscale. To better understand these materials, we combine optical spectroscopy and scanning- probe method develpment to study charge separation, recombination and transport as a function of thin film morphology and interfacial chemistry in thin films of organic semiconductors. Our group has pioneered new applications of scanning probe microscopy such as time-resolved electrostatic force microscopy (trEFM) and photoconductive atomic force microscopy (trAFM) to image charge generation, photocurrents, and trapping in nanostructured solar cells. In addition we use Dip-Pen Nanolithography to generate templates for controlling nanoscale morphology through surface chemistry (image above). Electrostatic force microscopy and conducting-probe AFM are used to characterize charge generation, transport, and recombination, with simultaneous spatial resolutions better than 50 nm, and time resolutions of tens of nanoseconds.
Light Harvesting, Ligands, and Lifetimes: Optoelectronic Properties of Colloidal Quantum Dots
Semiconductor quantum dots and colloidal nanocrystals are promising solution processable materials for use in energy efficient displays as well as photodiodes and solar cells (where infrared absorbing quantum dots might be used to harvest a wider range of the solar spectrum). We make and test quantum dot device, including quantum dot solar cells, apply optical spectroscopy including photoinduced absorption, single molecule optical spectroscopy, and scanning-probe microscopy to correlate the optical and electronic properties of single nanocrystals.
We study plasmonic applications in fields ranging from biological detection to solar energy. The local electromagnetic field enhancements the occur near metal nanoparticles can be used to tailor the optical properties of surrounding chromophores. We study the optical properties of colloidal metal nanoparticles coupled to organic and inorganic chromophores using single-particle spectroscopy including single particle darkfield scattering and time-correlated single-photon counting with an eye towards applications in sensing, LEDs, and solar cells. We compare experiment with electrodynamics calculations. Images: (left) size and shape series of silver nanospheres and nanoprisms (right) finite difference time-domain (FDTD) calculation performed with Lumerical FDTD solutions package showing the large local field enhancements near a silver nanoparticle excited at the plasmon resonance.