A commonly used metric for rating solar cells is their external quantum efficiency (EQE), which is the fraction of incident photons of a particular energy that generate charge carriers. Although this ignores both the power produced by those charge carriers and the availability of photons of that energy in the solar spectrum, it provides a balanced, simple, and general method for comparing photovoltaic materials on a common footing. For this reason, efficient ab initio methods that can semi-quantitatively describe a material’s EQE are needed. To do so, the material’s optical absorption, charge carrier generation, and the resulting charge transport at a quantum level are needed to describe the EQE of a photovoltaic device. Here, we extend the non-equilibrium Green’s function formalism to describe the entire photoinduced quantum transport process within a device. As a proof of concept we present our results for a two-band tight-binding model and the density functional theory (DFT) hamiltonians calculated using a linear combination of atomic orbitals (LCAO) for (1) carbon chains acting as spin filters, (2) photoactive [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) molecular chains, (3) carbon nanoribbons (NRs), (4) single-walled carbon nanotubes (SWNTs) as ballistic conductors, and (5) the (100) and (101) facets of bulk silicon. Our results show that this method provides an efficient means for estimating the EQE of photovoltaic devices, allowing their design in silico.

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https://us06web.zoom.us/j/5081440931

Meeting ID: 508 144 0931 

Seminar hosts: Neven Šantić i Matija Čulo