PVnegf - a tool for the simulation of photovoltaics at the nanoscale


Introduction

PVnegf simulates the operation of quantum photovoltaic devices based on 1D semiconductor heterostructures. In contrast to the drift-diffusion picture that is conventionally used to model solar cells, PVnegf relies on a fully quantum mechanical description of the electronic structure and of the optoelectronic processes on which device operation is based. It therefore provides not only external (measurable) device characteristics, such as JV-characteristics or luminescece spectra, but also microscopic internal quantities like the local density of states (LDOS), spectral density and current, local non-equilibrium occupation function for electrons and holes, position and energy resolved rates of generation, recombination and relaxation (via intraband scattering), local photon DOS and flux, and many more. Since the parameters provided relate only to the bulk component materials and the elementary interactions among charge carriers, photons and phonons, the complex physical behavior of the device under operation is not imposed in a phenomenological way, but emerges from first principles.

Features

Technically, PVnegf implements the non-equilibrium Green's function (NEGF) formalism for quantum transport of charge carriers in open systems in the presence of intra- and interband scattering. At this stage, it offers the following capabilities:
  • electronic structure: decoupled multi-band effective mass, multiband tight-binding*
  • electron-photon interaction: non-local coupling to classical field for absorption and stimulated emission, coupling to photon Green's function for spontaneous emission (SCBA), reabsorption* (photon recycling);
  • electron-phonon interaction: acoustic and polar-optical (SCBA), non-polar optical*, intervalley-scattering* (for indirect semiconductors like Si, Ge);
  • electron-electron interaction: Hartree/mean field level via self-consistent coupling to Poisson equation, GW self-energy* for intraband scattering;
  • excitons: absorption enhancement from Bethe-Salpeter equation for coherent polarization function*;
  • defects: microscopic equivalent to SRH recombination via multi-phonon relaxation*;
  • optics: classical light propagation via Lambert-Beer law and transfer matrix method, spectral absorption and emission from photon self-energy, full photon NEGF formalism*.
*not included in the initial binary release, will be added in subsequent releases

Download & Installation

Coming soon.

History

The code was originally written by Urs Aeberhard for his PhD work in the Condensed Matter Theory group at Paul Scherrer Institute (Switzerland). The simulation framework was then continuously extended during his time at IEK-5 Photovoltaik, Forschungszentrum Jülich (Germany).

How to cite

The essentials of this code have been outlined in several publications. Please cite at least one of them when publishing results obtained with the software.

The original paper introducing the NEGF approach for quantum well solar cells is:
[1] U. Aeberhard and R.H. Morf, Microscopic non-equilibrium theory of quantum well solar cells, Phys. Rev. B 77, 125343 (2008).

The first comprehensive overview over the NEGF modelling framework for solar cells is given in:
[2] U. Aeberhard, Theory and simulation of quantum photovoltaic devices based on the non-equilibrium Green's function formalism, J. Comput. Electron. 10, 394 (2011).

For a recent overview of applications to nanostructure photovoltaics:
[3] U. Aeberhard, Photovoltaics at the mesoscale: insights from quantum-kinetic simulation, J. Phys. D - Appl. Phys. 51, 323002 (2018).
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