Electrical Properties Of Organic Solar Cells Research Articles

Optical and electrical properties of short-pitch solar cells with finite-difference frequency-domain method

Organic solar cells (OSCs) have attracted intensive attention in recent years due to their distinct advantages of rich material resources, easy fabrication, and good flexibility. The standard structure of OSCs consists of an anode, an active layer and a cathode. Indium tin oxide (ITO) is often used as a transparent anode. However, the indium in ITO is not only very low in content, but also can penetrate into other layers of OSCs and affect the battery life. The ITO is not suitable for flexible OSCs because of its brittleness. Therefore, researchers have been trying to find alternatives to ITO, which should have transparent and flexible electrodes. The multilayer film consisting of MoO3/Ag/MoO3 is a very promising candidate as an alternative of ITO to work as the transparent anode in OSCs. However, in MoO3/Ag/MoO3 based thin OSCs structure, the absorption of light is quite poor. Here, we introduce a short-pitch metallic grating in which there are used the surface plasmon polaritons (SPPs) to enhance the light absorption of the active layer. The finite-difference frequency-domain method is used to solve the Maxwell's equations and semiconductor equations for revealing the optical and electrical properties of OSCs. As is well known, the contradiction between the long light absorption path and the short exciton diffusion length results in a relatively low power conversion efficiency (PCE) of the OSCs. Metallic gratings can be introduced into conventional OSCs for improving the light absorption due to the surface plasmon resonance. The light absorption can be enhanced compared with that in the conventional OSCs without metallic gratings. At the same time, the small periodic structure is introduced into the MoO3/Ag/MoO3 anode-based OSCs. The small spacing between gratings creates a strong interaction between two adjacent metal nanowalls. These nanostructures and metal nanostructures will further enhance the light absorption. In this work, it is proposed that short-pitch metallic gratings be introduced into the MoO3/Ag/MoO3 anode-based OSCs for improving the light absorption and PCE. It is found that the light absorption of plasmonic structure with short-pitch metallic gratings can be greatly enhanced compared with standard structure without metallic gratings. Meanwhile, with an optimal groove width of 4 nm, PCE is improved by 49% compared with the case with the planar structure. These results contribute to better developing the ITO free OSCs.

The Study of Optical and Electrical Properties of Short-Pitch Plasmonic Solar Cells

Metallic gratings have drawn great attention over the past few years due to effective light trapping and power conversion efficiency enhancement in organic solar cells (OSCs). Novel OSCs incorporated short-pitch metallic grating into the conventional OSCs as the back electrode is presented. The optical and electrical properties of OSCs are investigated by applying the finite-difference frequency-domain method. It is found that the light absorption at 400–650 nm in the active layer is strongly improved, compared with the standard structure without metallic grating. The underlying physical mechanism is due to the surface plasmon resonance and the interaction between two neighbor gratings, which undoubtedly enhances the electrical properties such as short-circuit current $(J_{\mathrm{SC}})$ , fill factor, and power conversion efficiency. Meanwhile, the optical and electrical properties of OSCs with different groove widths are also investigated. With an optimal groove width of 4 nm, the overall performance of OSCs is enhanced. This paper indicates that OSCs incorporated short-pitch metallic grating are promising candidates for high-performance OSCs.

MULTI-PHYSICAL PROPERTIES OF PLASMONIC ORGANIC SOLAR CELLS (Invited Paper)

(Invited Paper) Abstract|Organic solar cells (OSCs) have recently attracted considerable research interest. For typical OSCs, it is highly desirable to have optically thick and physically thin thickness for strong light absorption and e-cient carrier collection respectively. In the meantime, most organic semiconductors have short exciton difiusion length and low carrier mobility (1{3). As a consequence, the active layers of OSCs are generally thin with a thickness of a few hundred nanometers to ensure the e-cient extraction of carriers, hence limiting the total absorption of incident light. Optimizing both the optical and electrical (i.e., multi-physical) properties of OSCs is in demands for rationally designed device architectures. Plasmonic nanomaterials (e.g., metallic nanoparticles (4{6), nanorods (7,8), nanoprisms (9,10), etc.) have recently been introduced into difierent layers of multilayered solar cells to achieve highly e-cient light harvesting. The multilayered solar cells structures commonly have active layer, carrier (electron and hole) transport layer and electrode (anode and cathode). Through the localized plasmonic resonances (LPRs) (11{16) from metallic nanomaterials, very strong near-flelds will be generated, which can provide a large potential for enhancing optical absorption in the multilayered OSCs. Besides the optical efiects, it has been reported that metallic nanomaterials can modify the morphology, interface properties as well as the electrical properties of OSCs which will signiflcantly modify the performances of OSCs (17{23). In this article, the efiects of various optical resonance mechanisms and the theoretical studies of the multi- physical properties of OSCs will be reviewed. Meanwhile, the experimental optical and electrical efiects of metallic nanomaterials incorporated in difierent layers of OSCs will be studied. The morphology and interface efiects of metallic nanomaterials in the carrier transport layers on the performances of OSCs will also be described.