Research

Photovoltaics   Nanophysics   Light-Matter Interaction

Overview

Exploring and tuning light matter interaction has led to advances in fundamental science as well as in many applications. Micro and nanostructured materials can be used in order to manipulate optical properties and to confine light to a desired volume. In order to push energy conversion efficiency in solar energy conversion devices to the theoretical limits it is important to gain full control over the optical properties. The Saive research group develops light-management strategies that contribute to increased efficiency of photovoltaic and solar-to-fuel devices. Furthermore, we combine different material systems with complementary properties to develop hybrid devices that exhibit functionalities beyond existing technology.

Light-management strategies for solar energy conversion

Increasing the efficiency of solar energy conversion devices is a crucial step for energy cost reduction. The development of solar energy conversion devices such as solar cells and water splitting devices undergoes different stages. It usually starts with a new material system and the investigation of its fundamental properties and capabilities. In the second stage a device with the desired functionality is designed and material and interface properties are optimized to improve the performance. In order to push the performance to its theoretical limits it is necessary to optimize the light-management in a further step. Light-management strategies include all measures that are taken in order to achieve maximum light absorption and maximum quasi Fermi level splitting within the active absorber materials. It includes the design of optimized contacts that are as transparent as possible while ensuring good conductivity and also light-trapping strategies that are extremely important in thin film solar cells.

In highly developed technologies such as state-of-the-art silicon photovoltaics the light absorption is already close to the limits. However, in emerging technologies including thin film silicon, Perovskite solar cells or water splitting devices novel strategies need to be developed. For example in Perovskite solar cells, there is tremendous room to improve front superstrate and contact layouts as well as back scattering layers. Applying existing light management strategies to these cells would yield an immediate increase in short circuit current density.

In water splitting devices it is important to design surfaces that feature high catalyst surface coverage while still allowing as much light as possible to enter the device. Micro- and nanostructured optical designs fulfill these requirements. The Saive research group develops new light-management strategies but also adapts existing strategies to these emerging technologies.

Strong industrial interest in rising in the field of bifacial solar cells. Due to the acceptance of photons at front and rear side, the power output can be significantly enhanced without increasing the use of expensive absorber materials. The properties of the surroundings such as the spectral dependent albedo play a crucial role for the power output. We use our strong background in light-management to develop industrially relevant strategies for performance enhancement of bifacial solar cells.

In all our projects, we combine computational optical and electronic simulations with experimental prototyping for most efficient device design. State-of-the art nanotechnology such as electron beam lithography, imprint lithography and nano-3D-printing is applied in order to push the performance to its limits.