Nanohole Design for High Performance Polymer Solar Cell Doha M.A.Rahman 1 , Mohamed Farahat O. Hameed 1,2 , Member, IEEE, S. S. A. Obayya 1 , Senior Member, IEEE 1 Center for Photonics and Smart Materials, Zewail City of Science and Technology, Giza, Egypt sobayya@zewailcity.edu.eg 2 Mathematics and Engineering Physics Department, Faulty of Engineering, Mansoura University, Mansoura, Egypt Abstract –A novel design of nanohole polymer solar cell (NHPSC) is reported for light trapping improvement. The proposed design has shown a considerable enhancement in the optical and electrical parameters of the polymer solar cell based on a conventional blend of poly-3-hexylthiophene/ [6, 6]-phenyl- C61-butyric acid methyl ester (P3HT:PCBM) as an active material. In this study, 3D finite difference time domain method is used to simulate the light absorption in the nanohole structure. In addition, an electrical model is developed to calculate the electrical parameters of the polymer solar cell. The reported design has shown 28% improvement in short circuit current density and overall efficiency alike. Index Terms – solar cell; nanohole; opto-electrical model I. INTRODUCTION In recent years, organic solar cells (SCs) have gained enormous interest due to their low cost, flexibility and large area [1]. However, the low efficiency of organic solar cells which around 5% [2-5] remains a massive challenge. As a result, a number of different techniques has been investigated to improve the efficiency of the organic solar cell such as; localized surface plasmon on metal nanoparticles [3, 4] and plasmonic cavity [5]. Currently, nanostructures have grown as the main building block to construct light-trapping which can improve the absorption in the active materials as well as the overall efficiency of the solar cell [6].The use of sub- wavelength nanostructure has gained a great attention due to its high ability of light trapping by increasing the optical bath length. Consequently, the photon absorption inside the active material can be enhanced [7]. Electrical modeling is one of the most important aspects for studying the performance of the solar cell and calculating the power conversion efficiency. Therefore, a number of studies has been reported to obtain the electrical parameters of the solar cell [2, 8]. In this paper, the optical and electrical properties for nanohole (NH) polymer solar cell, based on poly-3- hexylthiophene/ [6, 6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as an active material, have been investigated. The finite difference time domain method is used to obtain the optical properties of the suggested nanohole polymer solar cell (NHPSC) structure which shows a dramatic enhancement in the light absorption with a significant refinement in the short current density and overall efficiency. In addition, an electrical model based on single diode model and electron diffusion differential model [8] has been developed to calculate the electrical parameters and overall efficiency. The numerical results reveal that the proposed new design has the potential to improve the short circuit current and overall efficiency by around 28% compared to the conventional photonic crystal (PC) polymer SC [6]. To the best of our knowledge, this is the first time to introduce a complete opto-electrical model for polymer solar cell to study its optical and electrical properties and obtain the power conversion efficiency of the cell. Fig. 1 Schematic diagram of polymer solar cell based on (a) conventional PC [6] and (b) proposed NH structure II. DESIGN CONSIDERATIONS The conventional polymer solar cell structure consists of glass substrate coated by anode layer of Indium tin oxide (ITO) and hole block layer of PEDOT:PSS as shown in Fig. 1 (a). In addition, P3HT:PCBM nanostructure photoactive layer is coated over the PEDOT:PSS layer. Moreover, a layer of nano crystalline Zinc oxide (nc-ZnO) is used as an electron transport layer. Finally a layer of aluminium (Al) is used as a cathode. It should be noted that, a flash flat layer of P3HT:PCBM is needed to prevent the direct contact between the PEDOT:PSS layer and the (nc-ZnO) layer [9]. In this investigation, our proposed design has a square NH lattice with periodicity (p) as shown in Fig. 1 (b). The NH with height (h) and width (w) is embedded into the photoactive layer P3HT: PCBM. The NH structure is periodic along x and y directions. Therefore, to save the simulation time, we simulate only one unit cell of the structure and the boundary conditions are taken as anti-symmetric along x-direction and symmetric along y-direction. In addition, perfect matching layers (PML) boundary conditions are used along z-direction. In this study, a plane wave is incident normally on the glass substrate where the reflection from the air-glass interface is overridden. NUSOD 2014 57 978-1-4799-3682-3/14/$31.00 ©2014 IEEE