Investigation of VOPcPhO as an acceptor material for bulk heterojunction solar cells Shahino Mah Abdullah a,1 , Zubair Ahmad a,⇑,1 , Fakhra Aziz b,1 , Khaulah Sulaiman a,1 a Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur, Malaysia b Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi 23640, Pakistan article info Article history: Received 11 June 2012 Received in revised form 19 July 2012 Accepted 19 July 2012 Available online 9 August 2012 Keywords: Donor–acceptor blend P3HT VOPcPhO Solar cell abstract In this study, we have successfully demonstrated a new system of donor–acceptor blend for bulk heterojunction solar cells of poly(3-hexylthiophene) (P3HT) by using vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO) as acceptor material. A broad absorption over the whole visible range (450–750 nm) is achieved. Utilizing this blend sys- tem in solar cell fabrication, ITO/PEDOT:PSS/P3HT:VOPcPhO/Al solar cells have been fabri- cated and characterized in open air. A maximum power conversation efficiency up to 1.09% has been recorded. To confirm the charge transport, the electron and hole mobility of VoPc- PhO has been measured. The results show that the VoPcPhO has bipolar transport and can act as an electron as well as hole transporting material. The electron mobility is compara- ble with hole mobility. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Organic solar cells have become an attractive proposi- tion due to the availability of a variety of inexpensive materials which possess tunable properties and can be eas- ily incorporated in the fabrication procedure [1]. However, the quest for a material that will solve the problems of low efficiency and poor reliability and instability is still an ac- tive research area [2]. Since the last decade, polymers have attracted remarkable interest due to the emerging of new polymer materials with interesting properties suitable for flexible, light weight and high efficiency all-solution – pro- cessed solar cells [3–8]. Maximum power conversion effi- ciency up to 9% has been reported recently for a polymer solar cell [9]. Among the many polymers, poly(3-hexylthi- ophene) (P3HT) has acquired a prominent place as an effi- cient polymer matrix that has a wide absorption range of the solar spectrum and comparably high conductivity [10]. Over the past decade, research has focused on P3HT as a donor material, and the high-performance bulk het- erojunction solar cells have been fabricated from blends of P3HT and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) [11–14]. However, there are very few reports on non-fullerene alternatives to PC BM in solution processed bulk-heterojunction solar cells [15–19]. Even though P3HT has shown a wide absorption range towards sunlight, there is some portion of solar spectrum which needs to be covered. Several attempts have been made to overcome this limitation, which include modification of the chemical structure of electron-donor and electron-acceptor materi- als [6,20], the plasmonic effect within organic tandem solar cells [21,22] and the introduction of a ternary system, in which a third organic compound is added to a binary bulk heterojunction [23,24]. All these methods used for enhanc- ing solar absorption spectrum have been known to im- prove the performance of solar cells. The materials from the phthalocyanine family have also been reported to improve absorption of the solar spectrum [23,25]. The phthalocyanines exhibit very intense absorp- tion in the UV–Vis spectral region which makes them suitable for the optoelectronic applications [26,27]. Re- cently it has been shown that the electron mobility in 1566-1199/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.orgel.2012.07.030 ⇑ Corresponding author. Tel.: +60 3 79674147; fax: +60 3 79674146. E-mail address: zubairtarar@gmail.com (Z. Ahmad). 1 All authors have contributed equally. Organic Electronics 13 (2012) 2532–2537 Contents lists available at SciVerse ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel