Efficient first-principles calculation of phonon assisted photocurrent in large-scale solar cell devices

We present a straightforward and computationally cheap method to obtain the phonon-assisted photocurrent in large-scale devices from first-principles transport calculations[1]. The photocurrent is calculated using nonequilibrium Green's functions with light-matter interaction from the first-order Born approximation while electron-phonon coupling (EPC) is included through special thermal displacements (STD). We apply the method to a silicon solar cell device and demonstrate the impact of including EPC in order to properly describe the current due to the indirect band-to-band transitions. The first-principles results are successfully compared to experimental measurements of the temperature and light intensity dependence of the open-circuit voltage of a silicon PhotoVoltaic (PV) module[1]. We use the method to predict the solar cell efficiency of new Janus type 2D devices[2] and show that they outperform the silicon PV module. This work represents a recipe for computational characterization of future PV devices including the combined effects of light-matter interaction, phonon-assisted tunneling and the device potential at finite bias from the level of first-principles simulations.
[1] Palsgaard, M., et al. Phys. Rev. Appl. 10, 014026 (2017)
[2] Palsgaard, M., et al. Nano Lett. (2018)