Functionalized silicon nanowires/conjugated polymer hybrid solar cells: Optical, electrical and morphological characterizations N. Chehata a,n , A. Ltaief a , E. Beyou b , B. Ilahi c , B. Salem d , T. Baron d , P. Gentile e , H. Maaref c , A. Bouazizi a a Equipe Dispositifs Electroniques Organiques et Photovoltaïque Moléculaire, Laboratoire de la Matière Condensée et des Nanosciences, Faculté des Sciences de Monastir, Université de Monastir, 5019 Monastir, Tunisia b Ingénierie des Matériaux Polymères, Université Claude Bernard Lyon 1,15 boulevard Latarget, 69 622 Villeurbanne Cedex, France c Laboratoire de Micro-optoélectronique et Nanostructures, Faculté des Sciences de Monastir, Université de Monastir, 5019 Monastir, Tunisia d Laboratoire des Technologies de la Microélectronique, CEA Grenoble, 17 Rue des Martyrs, Grenoble, France e Laboratoire Silicium Nanoélectronique Photonique et Structures, CEA Grenoble, 17 Rue des Martyrs, Grenoble, France article info Article history: Received 20 April 2015 Received in revised form 11 August 2015 Accepted 13 August 2015 Available online 21 August 2015 Keywords: Organic compounds Composites Luminescence Optical properties Electrical properties abstract We investigate the effects of Si nanowires surface modification with polystyrene (PS) on the performance of bulk heterojunction hybrid solar cells based on poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and PS-SiNWs. The optical, electrical and morphological properties of these hybrid nanocomposites have been investigated. Due to charge transfer efficiency, improved electrical coupling between SiNWs and MEH-PPV and homogeneous dispersion of functionalized SiNWs, the performance of studied photovoltaic structure shows a significant improvement with the progressive addition of PS- SiNWs. With polystyrene surrounded SiNWs as acceptor materials, the device typically shows a J SC of 7.36 mA/cm 2 , V OC of 0.87 V and a FF of 48% for the composition MEH-PPV:PS-SiNWs (1:4). & 2015 Elsevier B.V. All rights reserved. 1. Introduction Intensive research has been conducted to develop low-cost photovoltaic (PV) technologies, and organic photovoltaics (OPVs) may be one of the most promising solutions [1–4]. Conjugated organic polymer solar cells are particularly attractive because of their ease of processing, mechanical flexibility and potential for low cost technology of large areas [5–7]. A significant progress in bulk hetero-junction (BHJ) polymer solar cell technology, com- posed of interpenetrating network of donor polymer and electron acceptor material, has been achieved in the last decades [8–12].A large variety of donor and acceptor materials have been tested. But, the reported efficiencies are not high enough to allow direct competition against mature photovoltaic technologies [13]. The recent combination of organic and inorganic materials to form organic–inorganic hybrid solar cells may pave the way toward the improvement of PV performance [14–17]. The hybrid BHJ approach allows one to overcome the main intrinsic limitations of con- jugated organic polymers used in organic solar cells; the quite poor charge carrier mobility (typically 10 À7 –10 À3 cm 2 /vs) [18] and relatively rapid recombination process to the detriment of exciton dissociation, by providing high-mobility pathway from the active interface to the electrodes for carriers and insuring a balanced con- sideration of charge carriers mobility. When silicon nanowires are incorporated as acceptor material within donor polymer matrix, the resulting hybrid structure will benefit of the particular structure and nature of these 1D inorganic nanomaterials mainly: the high electron mobility of this class of inorganic semiconductors and the big surface area for contact with the donor polymer whilst their nanostructure. Most recently, several research groups have demonstrated the ela- boration of polymer/SiNWs hybrid solar cells [19–24]. An improve- ment of performances of these hybrid devices has been achieved, where the FF factor was more important compared to pure organic devices [19–21]. It is crucial to emphasize that this enhancement is due solely to the structural self-assembly within the photoactive layer, without any additional device optimization, and that similar self- assembly processes may play a role in other organic/inorganic devices involving one-dimensional materials, including carbon nanotubes and other semiconductor nanowires. One of the most inconvenient in the incorporation of nanomaterials is related to the surface traps, created after nanomaterials synthesis [25]. Particularly, the intrinsic surface defects of Si nanowires will make the final power conversion effi- ciency of hybrid solar cells lower than their inorganic Si wafer based counterparts. These defects would trap photo-excited electrons, which Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence http://dx.doi.org/10.1016/j.jlumin.2015.08.020 0022-2313/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ216 73 50 02 76; fax: þ216 73 50 02 78. E-mail address: nadiachehata2@gmail.com (N. Chehata). Journal of Luminescence 168 (2015) 315–324