Influence of electrode degradation on organic solar cells functioning – a computational study

Abstract

Recently, organic solar cells (OSC) have reached the efficiency of 10% becoming a reliable alternative to the conventional high cost inorganic solar cells. However, to gain a place in the competitive market of solar cells it is necessary to improve their lifetime. Due to the nature of the materials used, there are several degradation mechanisms [1] that lead to a decrease on device efficiency and thus to its failure, being of upmost importance to understand how they affect organic solar cells functioning. One of these mechanisms consists on electrodes degradation when in contact with air or water, leading to a change on electrode work function and thus of the energy levels at electrode/organic layer interface. As a result, the decrease on OSC efficiency has been attributed to a loss on the electrode´s ability in collecting charges from the active layer [2, 3]. However, it is unclear how a change on electrode’s work function affects the main optoelectronic mechanisms that rule the device performance [4], which can give some guidelines to prevent its failure. In order to clarify this issue we performed computational experiments with our improved mesoscopic model. Our results show that changing electrodes work function affects simultaneously all optoelectronic mechanisms that rule exciton and charges dynamics, and thus the device performance.