Polymer defect states modulate open-circuit voltage in bulk-heterojunction solar cells
- Photovoltaic and Optoelectronic Devices Group, Departament de Física, Universitat Jaume I, ES-12071 Castelló (Spain)
Defect states influence the operation of organic solar cells altering transport, recombination, and energetic mechanisms. This work investigates how processing conditions induce morphology-related, electrically active defects in the donor polymer of bulk-heterojunction solar cells. Structural order is inferred from absorption and X-ray diffraction data, while defect density is determined from capacitance methods. A correlation is observed between the polymer nanocrystallite size, the defect concentration, and the output voltage. For the case of poly(3-hexylthiophene), processing that promote crystallinity is beneficial for the device performance as it decreases the defect density (energy disorder) that finally enlarges the maximum achievable open-circuit voltage. Defect states within the effective bandgap modulate the downshift of the hole Fermi level upon illumination that in turn establishes the achievable open-circuit voltage.
- OSTI ID:
- 22253784
- Journal Information:
- Applied Physics Letters, Vol. 103, Issue 24; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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