We fabricated flexible transparent conducting electrodes by printing films of single-walled carbon nanotube ͑SWNT͒ networks on plastic and have demonstrated their use as transparent electrodes for efficient, flexible polymer-fullerene bulk-heterojunction solar cells. The printing method produces relatively smooth, homogeneous films with a transmittance of 85% at 550 nm and a sheet resistance ͑R s ͒ of 200 ⍀ / ᮀ. Cells were fabricated on the SWNT/plastic anodes identically to a process optimized for ITO/glass. Efficiencies, 2.5% ͑AM1.5G͒, are close to ITO/glass and are affected primarily by R s. Bending test comparisons with ITO/plastic show the SWNT/plastic electrodes to be far more flexible.

In order to realize enhanced spectral coverage in organic photovoltaic devices, the authors have stacked a zinc phthalocyanine:C60 based cell on the top of a poly-3-hexyl-thiophene:[6,6]-phenyl C61-butyric acid methyl ester layer using a 1nm thick Au intermediate recombination layer. Such tandem devices comprising active materials with complementary absorption spectra exhibit a short circuit current (Isc) of 4.8mAcm−2, an open circuit voltage (Voc) of 1020mV, and a fill factor of 0.45. Measurements of the photocurrent versus wavelength of the incident light show that photons are converted into charge carriers from 400 to more than 800nm. Further optimization of the respective layer thicknesses may lead to high efficiency devices.

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