Wavelength influence on the photodegradation of P3HT:PCBM organic solar cells

• Influence of incident wavelength on the degradation process of organic solar devices.
• PCE and ISC show a decreasing evolution vs. incident energy and number of photons.
• A first simple empirical model describes the photodegradation process mechanism.
• The wavelength of the incident radiation is more relevant than the energy received.

Stability of emerging organic and hybrid photovoltaic solar cells is still the main drawback for a market penetration of this technology. In this article, a study on the photodegradation of standard architecture P3HT:PCBM organic solar cells as a function of the incident radiation wavelength is presented. The organic solar cells were tested without encapsulation in order to accelerate the degradation process. By analyzing the evolution of power conversion efficiency and short circuit current as a function of the incident energy and number of photons, it was found that blue (400–510 nm) and ultraviolet (310–410 nm) wavelengths are the most harmful, latter being the radiation that induces a faster degradation of the devices. However, the additional contribution of the blue wavelength to degradation represents a significant problem, since this radiation generates an important part of the photocurrent. While adequate filters could avoid the UV degradation without a significant decrease in the organic solar cell performance, the impact of blue radiation reduction poses a more difficult challenge.