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We present a systematic study of the effects of post-fabrication annealing on the performance of photovoltaic devices that incorporate a photoactive donor–acceptor dispersed heterojunction system. Solar cells have been fabricated based on poly(3-octylthiophene) as donor (D) and single-wall carbon nanotubes as the electron acceptor (A) with a PEDOT:PSS hole transport layer. A post-fabrication annealing treatment was carried out at a temperature range of 40–200 C. The best results were obtained at 120 C; at this temperature the cell shows a short circuit current, Isc = 0.5 mA cm−2, an open circuit voltage, Voc = 0.75 V and a fill factor, FF = 0.6, resulting in a power conversion efficiency of η = 0.22% under AM 1.5 (100 mW cm−2) white light illumination. The annealing treatment led to a doubling of the power conversion efficiency. This was attributed to a better charge carrier transport in the polymer matrix and more effective charge separation and collection. [ABSTRACT FROM AUTHOR]

We report the direct measurement of electrical transport through rod-like polymer molecules, of poly(ethyl propiolate) (PEP), utilizing single walled carbon nanotubes (SWNTs) as electrodes. The electrical properties of the devices were measured (i) before cutting a SWNT, (ii) when a SWNT was cut and (iii) after PEP deposition into the nanoscale gap in a cut SWNT. The gate-dependent electrical properties showed a reduction in current from Ion = 2.4 x 10[?]7 A for SWNT devices to Ion = 3.6 x 10[?]9 A for PEP bridge devices, both with the ON/OFF ratio of 104. Similarly, metallic SWNT devices showed a reduction in current from a few hundreds of uA for a SWNT device to a few nA for a PEP-SWNT structure. The current density of a single PEP molecule is 105-106 A cm[?]2, which is relatively high, indicating that the PEP molecule can carry significant current. Use of SWNT electrodes was seen to be an effective method of contacting PEP nanorods to facilitate electrical measurements. [ABSTRACT FROM AUTHOR]

We examine the dark and the illuminated current-voltage (J-V) characteristics of poly(3-octylthiophene) (P3OT)/single-wall carbon nanotube (SWNT) composite photovoltaic cells as a function of SWNT concentration. Using an exponential band tail model, the influence of SWNT concentration on the J-V characteristics of the cells is analysed in terms of corresponding parameters such as effective hole mobility, short-circuit current, and open-circuit voltage. For the device with optimum 1% SWNT concentration, the increased photoresponse ([?]500 times) as compared to the pristine P3OT cell can be attributed partly to the increase ([?]50 times) in effective hole mobility, due to the reduction of localized states of the pristine P3OT matrix, and partly to the enhanced exciton extraction at the polymer/nanotube junctions. [ABSTRACT FROM AUTHOR]