Degradation Mechanisms of Organic Solar Cells
Abstract
Organic solar cells are of majority concern for future electrical power generation because of low-cost, lightweight and flexible production. Stability and degradation is of paramount importance in organic solar cells. Depending on the significance of air exposure, the degradation of organic solar cells can be divided into extrinsic and intrinsic degradation. Organic solar cells often suffer from degradation in oxygen and water. Intrusion of oxygen and water are the principal causes of extrinsic degradation. In this study, we discuss the recent developments of organic solar cell materials and summarize recent improve of organic solar cells with emphasis on the extrinsic degradation that specially related to oxygen and water.
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Introduction
Organic solar cells (OSCs) are considered to be a green solar energy technology. OSCs are attractive mainly because they can be fabricated from various organic compounds with modifiable structures and exhibit excellent flexibility, high power conversion efficiency (PCE) under low light irradiation, and promising see-through power-generation windows. Over the course of the past few years, various aspects of organic solar cells have been extensively studied, including synthesis and application of new materials, modeling of physical processes, large-scale manufacturing, stability improvement, etc. [1]. The research trajectories of OSCs have been described in various reviews [2-6]. The ultimate aim of organic solar cell research is to realize efficient solar energy conversion. In the past two decades, OSC efficiency has been remarkably improved through new approaches such as using fullerene electron acceptors [7,8], and broadening OSC absorption bands within the solar spectra [9]. The total energy output of a fabricated solar cell equals the product of its efficiency and lifetime. Therefore, stability is an important OSC property that impacts the value (yield over cost) of an OSC system as current energy production is largely limited by the low durability [10]. Thanks to persistent efforts, our understanding of the degradation of OSCs has been significantly deepened. Numerous structures have been developed to protect OSCs from degradation and the shelf lives of unencapsulated organic solar cells have been improved to thousands of hours. In addition, the working lifetime, of encapsulated organic solar cells under continuous irradiation, has improved. [6]
Conclusion
In this study, degradation of organic solar cells induced by oxygen and water is discussed and literature survey has shown that oxygen is more dominant as a parameter of degradation. In future studies it is necessary to determine how these parameters affect the efficiency of solar cells and how long does it take newly developed coatings to display activity.