Optical Characterisation and Modelling of Films and Organic Solar Cells

Abstract

This thesis describes the optical characterisation and modelling of films and organic solar cells. Different organic solar cell layer films were deposited on glass substrates and their optical constants were determined. Optical characterisation involved reflection and transmission measurements for each layer film. Reflection and transmission measurements were used for fitting dielectric functions of the films using CODE software in order to determine complex optical constants for each layer material. Bruggeman’s effective medium approach was used to obtained optical constants of two-phase composite materials from their constituent materials. Obtained optical constants for each organic solar cell layer were used to simulate the whole organic solar cell multilayer system using the transfer matrix formalism (TMF). The transfer matrix method used considers the interference in the multi-layer system and the multiple reflection and transmission in both the millimeter sized glass substrate and the nano-meter sized layers. From the simulation, a simplified method of determining optimal active layer thickness, maximum current density and absorption in the organic solar cell photo-active layer was formulated. Results produced help understand the optical behaviour of light interaction with an organic solar cell multi-layer system and can be used in the performance improvement of organic solar cells.