Enhanced efficiency of polymeric solar cells via alignment of carbon nanotubes

Abstract

Carbon nanotubes (CNTs) are well-known electron acceptor materials for use in optoelectronic devices due to their appropriate electronic properties. In this work, we report on their use as a part of the multi-component active layer in organic solar cells to provide better transport of photogenerated charges. To optimize transport, orientation of CNTs perpendicular to the electrodes of solar cells with an active layer of poly(3-hexylthiophene)-CNT-(6,6-phenyl C 61 butyric acid methyl ester) (P3HT-CNT-PCBM) composite is preferable. In order to achieve this preferred orientation by applying an electric field on the device electrodes, polarization of CNT solutions was studied using dielectric spectroscopy. We find that an improved orientation can be achieved with a high-frequency AC electric field due to the alternating force exerted rapidly on field-induced dipoles of the nanotubes. Following these experiments, the orientation method was applied to organic solar cells with a sandwich structure in which the active layer consists of P3HT-CNT-PCBM. The electric field was applied continuously on the electrodes during annealing at a temperature near the glass transition of the polymer matrix. We demonstrate that a significant increase in cell performance (i.e. open-circuit voltage = 0.61 V, efficiency = 4.53%, fill factor = 0.46) can be achieved, which may signify a better path created by the oriented nanotubes for carrier transport to the electrodes.

Organic solar cell materials and active layer designs—improvements with carbon nanotubes: a review

“…SWNTs functionalized with phthalocyanine‐pyrene conjugates have also been utilized by Guldi and coworkers in dye‐sensitized solar cells 77. Two different approaches published by us of this paper, discussed further, show that the use of SWNTs improves the photovoltaic properties of efficient polymer solar cells by structuring the BHJ active layer 78, 79. However, the use of CNTs in organic photovoltaics is not limited to SWNTs as demonstrated by the incorporation of PCBM‐functionalized multi‐walled carbon nanotubes (MWNTs) in PSCs 80.…”

“…Significant improvement of the I SC of P3 HT:PCBM solar cells has been obtained by the Plastic Optoelectronics Group of Limoges University, adding a small amount (0.1 wt%) of SWNTs in the solution and performing their orientation during the annealing process 79. The initial average cell efficiencies before annealing, around 2.5%, have been enhanced to 4.4% with 10 MHz electric field application.…”

Carbon nanomaterials for photovoltaic process

“…The PCE can be further enhanced by improving the alignment of CNTs. The orientation of the CNTs can be manipulated by a high-frequency AC electric field [275]. When CNTs was perpendicular to the electrodes, the PCE of the P3HT/CNT/PCBM device approached 4.53%.…”

Increase of open circuit voltage of polymer bulk heterojunction solar cell by functionalized single walled carbon nanotubes

“…8 Using a different strategy based on the alignment of the tubes, Radbeh et al also reported a significant improvement of BHJ solar cells efficiency (4.53% reported). 9 However, despite many attempts, recent systematic studies on acid shortened tubes tend to show that SWCNTs degrade the performances of BHJ solar cells. 10 In the present paper, we report on the achievement of large open circuit voltage V oc over 0.8 V, together with decent fill factor and large short circuit current, through the incorporation of high pressure CO conversion (HiPCO) ester functionalized SWCNT into a poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl) propyl-1-phenyl [6,6] Preparation of SWCNT-CO 2 H 2 2 SWCNTs 1 of 100 mg were stirred in 100 mL aq.…”