Degradation of organic photovoltaic devices: a review

Organic solar cells are considered as low-cost photovoltaic technology driven by potentially reduced cost production via high throughput processes, such as printing and lower cost of starting materials. However, commercial realization of this technology is hindered by poor device lifetimes due to environmental degradation of the devices. Under standard test conditions, these devices show lifetimes much shorter in comparison with conventional silicon or other inorganic thin-film solar cells. The lifetimes of organic solar cells are strongly dependent on device processing, measurement (temperature, humidity and light intensity) and encapsulation conditions in addition to intrinsic nature of the constituent materials and their reactivity with each other. Recently, there has been a conscious effort to improve the lifetimes of organic solar cells and strategies such as incorporation of oxide buffer layers, change in the device architecture to inverted geometry and improved materials have been demonstrated to result in improved device lifetimes. In this manuscript, the authors present a review of the degradation in organic solar cells and associated mechanisms, approaches undertaken to improve the device reliability characteristics and lifetimes, the methods to study degradation and finally a brief discussion on encapsulation of the devices.