Ultrafast spectroscopy of organic semiconductors

Summary form only given. Ultrafast electronic dynamics of high purity molecular crystals are studied by transient photomodulation spectroscopy. Free and trapped excitons are characterized by their unique transientabsorption and stimulated emission bands. Our results provide several insights into the gain dynamics of these materials and help the realization of an electrically driven organic laser. We study ultrafast relaxation between different excited states in molecular semiconductors and conjugated polymers using a novel ultrafast spectroscopy. The new technique utilizes two excitation pulses and one probe pulse, which are independently tunable across the entire visible and near infrared spectral range. We find that strongly bound excitons are the primary photoexcitations and intramolecular internal conversion is the dominant relaxation mechanism in the organic semiconductors.