Solar-Absorbing Materials

NREL's materials discovery and design researchers work to discover new light-absorbing semiconductors and develop existing absorbers to enable technologies such as thin-film photovoltaic (PV) devices and photoelectrochemical (PEC) cells.

This research area focuses on the initial synthesis of thin-film absorber materials in unconventional chemistries (e.g., complex phosphides, chalcogenides, oxides, and nitrides) and measurement of their properties (e.g., optical absorption, electrical conductivity, work function, and photoexcited carrier lifetime). Such research is the first step toward any material's practical use in PV or PEC devices.

Light Absorber Discovery

As primary single-junction PV absorber technologies (e.g., silicon, copper indium gallium selenide, and cadmium telluride) mature, it becomes increasingly important to consider alternative methods to increase the solar cell conversion efficiency. Because of this, materials discovery research at NREL is increasingly applied toward materials with wider bandgaps, for example in the 1.5–2.2 eV range, for integration with conventional absorbers in next-generation multijunction PV devices.

These wider-gap absorbers are also important as photoelectrodes in PEC cells for H₂ generation and CO₂ reduction to liquid fuels. Our PEC photoactive materials research focuses on using established semiconductor processing techniques to improve structural quality and increase performance of emerging light absorber materials for PEC cell applications. We also discover brand new materials for these (photo)electrochemical applications in collaboration with theoretical scientists, mainly focused on the photocathodes for carbon dioxide reduction, as well as complementary photoanodes.

For more information, see:

Low-Temperature Synthesis of Stable CaZn₂P₂ Zintl Phosphide Thin Films as Candidate Top Absorbers, Advanced Energy Materials (2024)

Epitaxial ZnGeP₂ Thin Films on Si and GaP by Reactive Combinatorial Sputtering in Phosphine, Crystal Growth & Design (2022)

Zinc Titanium Nitride Semiconductor Toward Durable Photoelectrochemical Applications, Journal of the American Chemical Society (2022).

Photovoltaic Devices

The ultimate goal of PV materials research is the practical application of new materials in useful devices such as solar cells. There is a myriad of interesting scientific challenges that arise from materials interactions, such as those associated with integrating multiple materials with optimal properties into a single device. These include measurements of materials band offsets.

For more information, see:

Codesigning Alloy Compositions of CdSe_yTe_1-y Absorbers and Mg_xZn_1-xO Contacts to Increase Solar Cell Efficiency, Solar RRL (2022)

Review of ZnSnN₂ Semiconductor Material, Journal of Physics (2020)

Research Update: Emerging Chalcostibite Absorbers for Thin-Film Solar Cells, APL Materials (2018).

Transparent Conductors

Wide-bandgap semiconductors are essential for electronic devices and energy applications because of their high optical transparency, controllable carrier concentration, and tunable electrical conductivity. Such transparent conductors, most commonly oxides, are used as contacts in thin-film PV and PEC cells.

For more information, see:

Nitrogen Stabilizes the Wurtzite Polymorph in ZnSe_{1− x}Te_x Thin Films, Journal of Materials Chemistry C (2022)

Prediction and Realisation of High Mobility and Degenerate P-Type Conductivity in CaCuP Thin Films, Chemical Science (2022)

Mg_xZn_{1− x}O Contact to CuGa₃Se₅ Absorber for Photovoltaic and Photoelectrochemical Devices, Journal of Physics: Energy (2021)

Wide Band Gap Chalcogenide Semiconductors, Chemical Reviews (2020).

Projects

The work on new light absorbing materials is funded by the U.S. Department of Energy (DOE) through the Office of Sciences, Basic Energy Sciences and through the Office of Energy Efficiency and Renewable Energy, Solar Energy Technology Program.

Research Collaborators

Contacts