Elizabeth R. Young Seminar

From Photodynamic Therapy to Photovoltaics: Photophysics of Pd(II)biladiene and Charge Carrier Dynamics in Thin Films of Light Harvesting Sb2S3

Elizabeth R. Young

Solar light harvesting and interconversion of solar energy into either electricity or driving force for small molecule activation reactions are critical to the production of energy and other processes that our society requires to function. In this talk, I will discuss two project united by photochemistry, each with their own application. In the first vignette, I will discuss a porphyrinoid complex, called a Pd(II)biladiene, This Pd(II)biladiene moiety was designed for use as a photosensitizer drug for photodynamic therapy. Up until this point, the excited-state dynamics of such biladiene complexes have been virtually unexplored. During our work on this moiety, we discovered that while excitation into the lowest-energy absorption feature of the Pd(II)biladiene complexes produces expected photophysics, interestingly, excitation into higher-lying excited states resulted in an additional, unexpected lifetime. I will discuss our work to propose the cause of this unexpected behavior. In the second vignette, I will discuss our recent work on stibnite (Sb2S3), which can be employed as the photoactive layer in next generation thin-film solar cells. Sb2S3 is of particular interest due to the suitable band gap of 1.7 eV and high absorption coefficient (1.8 × 105 cm–1 at 450 nm). I will present our work using transient absorption spectroscopy to directly observe carrier diffusion, electron transfer, hole transfer and charge recombination through uniform ultra-thin (< 3 nm) layers of insulating or transport materials deposited by atomic layer deposition (ALD) that are coupled to photo-active materials. Our results will be used to correlate the structure and function of material thickness and transport type to develop a fundamental, detailed, quantitative understanding of photo-induced ET dynamics through thin films of materials.