Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2022-2023)

This research program aims at exploring the relationship between "speed" (rate) of photo-induced electronic events and solar cell efficiency (number of produced electrons vs number of absorbed photons). These rates refer to photoinduced electron transfers from one ingredient (donor) to another (acceptor). Using inspiration from plants and photobacteria, the migration of electron (flow) accross the photosynthetic membrane occurs in an energy downhill process (thermodynamic cascade). These events of electron hopping from one site to another, after absorbing a photon from sun light, occurs in the short picosecond (ps) time scale (1 ps = 10 -12 second), then a little bit slower for the next step (also in the ps time scale). This process is such that the undesired return of the electron (called back electron transfer) occurs very slowly, securing the unidirectional flow of electrons. This inspiration is herein proposed in well-addressable layered structured solar cells. The proposed structure is composed of ITO (indium tin oxide; alternatively FTO: SnF 2 tin oxide) / nanoparticles of finite and controlled dimensions (of gold, silver and copper) / conjugated porphyrin dye-containing polymer / reduced graphene oxide or reduced graphene / aluminum. Each ingredient can be adjusted (nature of the nanoparticles and their sizes, nature of the polymers to adjust their facility to absorb light, including a part of the near-infrared for better photon harvesting) and to easily receive and release the electrons, conductivity of the reduced graphene oxide upon the "quality" of the reduced graphene. Quality refers to better conductivity; oxidized graphene could be considered a poor conductor if too oxidized). The rates for the electron cascade (excited nanoparticle to polymer to reduced graphene oxide) will be measured by ultrafast laser techniques. These techniques are fluorescence decays monitored by an ultrafast Streak camera (limit 5-10 ps), fluorescence up-conversion technique (limit 0.2 ps), and transient absorption spectroscopy (limit 0.05 to 0.1 ps). In order to establish a relationship between these rates and the solar cell efficiency, layered solar cells will be built with a well addressable structure (i.e. well defined layer thicknesses targetting 50 nm; 1 nm = 10 -9 m). The solar cells construction and testing and the measurements of the rates for electron transfers will be performed in Sherbrooke. The aims of this reasearch are what does it takes to 1) promote downhill thermodynamic ultrafast electron transfers (minimizing any undesired back electron transfers), 2) maximize all other possible photophysical processes (efficient energy migration in the desired direction) and 3) reduce any excited state annihilation at the same time. Such detailed photophysical and state-of-the-art investigations have never been performed in solar cell technology so far.