Aluminum Electrode Insulation Dynamics via Interface Oxidation by Reactant Diffusion in Organic Layers

Abstract

Appreciable progress has been achieved in the development of organic photovoltaics (OPV) over the last decade. However, further improvement of operational stability remains a challenge. In this contribution, focus is placed on corrosion and delamination of the metal contact, which are mainly caused by oxygen or water vapor ingress but in other cases also via mechanical wear and different thermal expansion coefficients. So-called pinholes and electrode edges provide pathways for ingress of water vapor and oxygen, which may attack the metalorganic interface. Thus, electrical insolation via formation of insulating metal oxide and concomitant mechanical delamination occurs. As charge injection and extraction is suppressed at insulated and delaminated areas, the active area contributing to power conversion gets reduced. This work links analytical and numerical predictions about the active area in contact with the electrode to experimentally observe dependencies. Spatially and time-resolved electroluminescence measurements provide information on location, size, and growth-rate of insulated areas. Area loss rates for dark spots depend either sub-linear (for early stages and edge-ingress) or linear (later stages) on time. The initial defect size has a clear impact on growth rates. Furthermore, it has possible to demonstrate titanium oxide interlayers to slow down this type of extrinsic degradation.

Fast and Nondestructive Failure Analysis of Organic Photovoltaic Modules for Low‐Light Harvesting: Coupling Variable Illumination Measurements to Electroluminescence Imaging

“…[24][25][26][27][28][29][30][31][32] Still, these approaches were not intended for low-light performance optimization but rather for device optimization under 1 sun [24][25][26][27][28][29][30][31][32] or in aging studies. [33][34][35] Furthermore, among the wide range of diagnosis tools developed for PV devices, electrical modeling approaches have been developed. PV cells have already been modeled by several equivalent circuits, [36][37][38] the simplest one being the so-called one-diode model.…”