SNIC SUPR
Computational X-ray spectroscopy for organic photovoltaics
Dnr:

SNIC 2019/3-330

Type:

SNIC Medium Compute

Principal Investigator:

Zilvinas Rinkevicius

Affiliation:

Kungliga Tekniska högskolan

Start Date:

2019-06-27

End Date:

2020-07-01

Primary Classification:

10402: Physical Chemistry

Allocation

Abstract

The present project aims to address the problem of stability of organic photovoltaics (OPVs) by computing X-ray spectroscopic signals for a set of OPV-related organic molecules and their possible photodegradation products. Even though the power conversion efficiencies of organic solar cells are not as high as in the case of silicon or perovskite solar cells, organic photovoltaics have several advantages over the former two technologies because they can be made into flexible devices by roll-to-roll printing techniques, on large scales and with low environmental impact. However, non-encapsulated OPVs, similar to perovskite solar cells, have one disadvantage in what regards their stability. When exposed to light in air, the power conversion efficiency of OPV devices strongly decreases due to several mechanisms, including photochemical reactions of the active layer materials with components of air, such as oxygen and water. In this project we aim to apply a very accurate method for computing different types of X-ray spectra for organic molecules used as electron donors or electron acceptors in OPVs. Both pristine materials, as well as possible photodegradation final products will be included. The method used here is the algebraic diagrammatic construction (ADC) scheme for the polarization propagator, which is an ab initio method based on the Møller-Plesset (MP) partition of the Hamiltonian. The different ADC flavors, obtained using increasing orders of perturbation theory, provide similar accuracy as the more familiar Coupled cluster (CC) methods, but at a lower computational cost. Among the molecules we plan to include are typical electron donors and acceptors, such as poly-3-hexyltiophene (P3HT) and the C60 fullerene, but also newly developed small organic electron acceptors used in fullerene-free OPVs.