Tandem organic solar cells containing plasmonic nanospheres and nanostars for enhancement in short circuit current density

Enhancing Efficiency of Nonfullerene Organic Solar Cells via Using Polyelectrolyte-Coated Plasmonic Gold Nanorods as Rear Interfacial Modifiers

Sufficient sunlight absorption and exciton generation are critical for developing efficient nonfullerene organic solar cells (OSCs). In this work, polyelectrolyte polystyrenesulfonate (PSS)-coated plasmonic gold nanorods (GNRs@PSS) were incorporated, for the first time, into the inverted nonfullerene OSCs as rear interfacial modifiers to improve sunlight absorption and charge generation via the near-field plasmonic and backscattering effects. The plasmonic GNRs effectively improved the sunlight absorption and enhanced the charge generation. Meanwhile, the negatively charged PSS shell ensured the uniform dispersion of the GNRs on the surface of the photoactive layer, optimized the interfacial contact, and further promoted the hole transport to the electrode. These concerted synergistic effects augmented the efficiency (10.11%) by nearly 20% relative to the control device (8.47%). Remarkably, the ultrathin (∼2.2 nm) organic layer on the surface of GNRs was closely examined by acquiring the carbon contrast image through energy-filtered transmission electron microscopy (EF-TEM), which clearly confirmed the coating uniformity from the side to end-cap of GNRs. The surface plasmon resonance (SPR) effect of the GNRs@PSS on the surface of the photoactive layer was unprecedentedly mapped by photoinduced force microscopy (PiFM) under the illumination of a tunable wavelength supercontinuum laser mimicking sunlight. Furthermore, investigations into the effect of size, surface coverage, and incorporation location of GNRs@PSS on the performance of OSCs revealed that the appropriate design and incorporation of the plasmonic nanostructures are crucial, otherwise the performance can be decreased, as evidenced in the case of front interface integration.

A New Type of Architecture of Dye-Sensitized Solar Cells as an Alternative Pathway to Outdoor Photovoltaics

The current investigation shows a possible new pathway for more efficient and cost-effective energy-harvesting photovoltaic devices. Our approach could permit all emerging technologies that are currently used for indoors and smart buildings to go a step forward and could be used for outdoor applications. The investigated architecture is a very promising geometry especially for Dye-Sensitized Solar Cells (DSSCs). It turns their main drawback, the lowering of their efficiency and lifetime when operating at high solar irradiation density, into an asset by increasing the total active area per horizontal unit area for light harvesting, while preserving the active elements from degradation and extending durable lifetime. The investigated architecture is based on a symmetric “U” type geometry, which is constructed by a highly reflective material on the inner surface. Solar irradiation is reflected internally at the bottom of the construction and splits towards two opposite sided solar cells; the two cells form a cavity where the solar light multiplies and is successively absorbed. Consequently, the vertically incoming irradiation is reduced when reaching the vertical internal sides on which the DSSCs are mounted. Thus, the solar cells operate at low light intensities, which provide significant lifetime extension and efficiency enhancement. Interestingly, the electrical energy per effective surface unit, which is produced by the two vertical DSSCs, is at least equal to that of a standalone, vertically irradiated cell. The advantage of the new architecture is that protects DSSCs from their degradation and deterioration, although the entire system operates under high illumination. This makes the cells more efficient outdoors, with a comparable performance to indoor conditions.

Synergetic effects of a front ITO nanocylinder array and a back square Al array to enhance light absorption for organic solar cells

Efficient light management is critical to obtain high performance for organic solar cells (OSCs), which aims to solve the contradiction between limited carrier extraction and light absorption for the normally employed photoactive layers generally having both short exciton diffusion lengths and low extinction coefficients. In this study, we introduce a simple and efficient light management structure consisting of a front indium tin oxide nanocylinder (ITO-NC) array and a back square Al array. Thanks to the synergetic effects of antireflection and light scattering induced by the ITO-NC array, together with the secondary scattering and localized surface plasmon resonance because of the square Al array, remarkably enhanced light absorption in a broad spectral range can be achieved. Taking the most investigated photoactive layer of the P3HT:PC₆₁BM blend as an example, simulation results reveal that, compared with the planar control device of the ITO/PEDOT:PSS/P3HT:PC₆₁BM(80nm)/ZnO/Al, the short-circuit current density and power conversion efficiency can be enhanced by 36.58% and 38.38% after incorporating the light management structure with the optimal structural parameters. Furthermore, good omnidirectional light management can be achieved for the proposed device structure. Given the excellent performance and simple structure, we believe that this study would provide a meaningful exploration of developing light management structures applicable for thin film-based optoelectronic devices.

Rigorous coupled-wave analysis of a multi-layered plasmonic integrated refractive index sensor

We apply the rigorous coupled-wave analysis (RCWA) to the design of a multi-layer plasmonic refractive index sensor based on metallic nanohole arrays integrated with a Ge-on-Si photodetector. RCWA simulations benefit from modularity, frequency-domain computation, and a relatively simple computational setup. These features make the application of RCWA particularly interesting in the case of the simulation and optimization of multi-layered devices in conjunction with plasmonic nanostructures, where other methods can be computationally too expensive for multi-parameter optimization. Our application example serves as a demonstration that RCWA can be utilized as a low-cost, efficient method for device engineering.