Radiation induced damage and recovery in poly(3-hexyl thiophene) based polymer solar cells

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Abstract
Polymer solar cells have been characterized during and after x-ray irradiation. The open circuit voltage, dark current and power conversion efficiency show degradation consistent with the generation of defect states in the polymer semiconductor. The polymer solar cell device remained functional with exposure to a considerable dose (500 krad (SiO2)) and showed clear signs of recovery upon removal of the irradiation source (degraded from 4.1% to 2.2% and recovered to 2.9%). Mobility-relaxation time variation, derived from J-V measurement, clearly demonstrates that radiation induced defect generation mechanisms in the organic semiconductor are active and need to be further studied. Optical transmission results ruled out the possibility of reduced light absorption and/or polymer crystallinity. The results suggest that organic solar cells are sufficiently radiation tolerant to be useful for space applications.