Abstract

Enhancing light absorption within thin film amorphous silicon (a-Si) solar cells should lead to higher efficiency. This improvement is typically done using various light trapping techniques such as utilizing textured back reflectors for pronounced light scattering within the cell thus achieving higher absorption. It is believed that embedding metallic nanoparticles (MNPs) inside the structure could increase light scattering. However, embedding MNPs can also cause significant structure defects and pronounced efficiency drop as well – it has been indicated by many experiments that disproved this belief. In search of ways to improve efficiency, we have investigated the impact of MNPs size, and location within the solar cell, in addition to the effect of defects, and doping levels on the overall efficiency. On the basis of our 3D multiphysics (optical-electric) modeling, we developed a design guideline for embedding these MNPs and reducing the impact of defects created in the embedding process. The results of simulations were compared to relevant measured data, and it showed a good agreement. Subsequently, models were used to predict performance, and over 30% improvement in solar cell efficiency (~13% is predicted), which is beyond the state of the art. This was predicted by optimizing the size and location of the MNPs and tailoring the doping levels to have better forward light trapping and absorption.

Abstract

Solar cells used in building integration of photovoltaic cells (BIPV) are commonly made from crystalline wafer cells. This contribution investigates the challenges and benefits of using bifacial solar cells in vertical installations. We show that those cells get up to 13% more irradiance compared to optimum tilted south facing monofacial modules in Germany. The role of the n-layer in thin amorphous bifacial single-junction cells intended to be used as bifacial cells in BIPV applications is investigated. In contrast to the superstrate cell design, a transparent n-layer and back contact play a key role to achieve high bifaciality. We therefore increased the transparency of the n-layer by adding CO2, increasing the PH3 flow in the deposition gas and tested different thicknesses. With those measures, we reached a bifaciality of 98% for short-circuit current density and 99% for open-circuit voltage.

Abstract

Ceramic multi-layer systems are the key components of solid oxide cells (SOC) to be used either for power generation or energy storage. Over the last decades continuous improvement in materials, architecture and manufacturing processes have been achieved to improve performance, durability and lifetime. The advanced concept of a metal-supported SOC where the functional ceramic layers are deposited onto a mechanically stable porous metal support is the most advanced approach for mobile application as auxiliary power units (APU) having strict requirements in terms of low volume, limited weight and improved ability for rapid start-up and thermal cycling. The paper provides an overview of the metal-supported cell development at DLR where functional layers are consecutively deposited by plasma spray technology onto a metal substrate. The current status of this development including materials aspects, stack technology and electrochemical performance is reported. When operating temperature is governed mainly by the electrocatalytic properties of the functional electrode materials and thickness of the electrolyte, thin-film electrolyte opens up the opportunity of low temperature operating SOC. Recently, further research efforts have started to develop a metal-supported cell with thin-film electrolyte. Hermetic thin films have been applied through PVD technology resulting in bilayer structured coatings. Recent results of this development are also presented. Document type: Part of book or chapter of book