DFT combined with the non equilibrium Green’s function (NEGF) formalism was f.ex. These effects can, however, be captured using atomistic models based on density functional theory (DFT). It is difficult to include important effects such as confinement of electrons and phonons, surface- and strain in the continuum models. Here it is stressed how the abundance of candidate materials together with the lack of efficient devices highlight the need for efficient predictive device calculations.Ĭontinuum models are used extensively in the field of PV to extract benchmark parameters from measurements on devices and to predict the performance of new device geometries Burgelman et al. Recently a review was published on the design of new materials using first-principles calculations Butler et al. The field of computational material science has seen massive progression and as a result the difference between system size and complexity attainable in simulations and experiments is becoming smaller every day. ( 2016).Ĭlearly there is still room for discovery of new materials to improve on the cost/efficiency relationship. In the last couple of decades many promising thin film absorber materials have been discovered, all of them with unique strengths and weaknesses.ĬdTe and CIGS (CuInGaSe 2) can produce high efficiencies, but include rare and toxic elements, CZTS includes only nontoxic earth abundant elements, but suffers from low efficiency and open circuit voltage ( V o c) Philipps and Warmuth ( 2017) Fthenakis ( 2004) Woodhouse et al. Photovoltaics (PV) represents a promising technology as a replacement for burning fossil fuels. This work represents a recipe for computational characterization of future photovoltaic 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. Our calculations illustrate the pivotal role played by EPC in photocurrent modelling to avoid underestimation of the open-circuit voltage, short-circuit current and maximum power.
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 module. 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 photocurrent is calculated using nonequilibrium Green’s function with light-matter interaction from the first-order Born approximation while electron-phonon coupling (EPC) is included through special thermal displacements (STD). We present a straightforward and computationally cheap method to obtain the phonon-assisted photocurrent in large-scale devices from first-principles transport calculations.