June 6, 2016 – Energy-sapping defects in solar cell material can be revealed with an unprecedented, dual-imaging method established by researchers at Oak Ridge National Laboratory. ORNL scientists scanned hybrid perovskite films to measure “dark” electronic trap states in complex photovoltaic materials, providing a visual tool for insight into more durable, high-performing devices. Their approach allows reliable and direct mapping of the poorly understood phenomenon hindering solar cell technology advances. The result can be considered an “efficiency map” of the material with energy leaks pinpointed. “With our imaging method, other researchers can now see, understand and ultimately address these trap states for better energy conversion efficiency of solar cell technology,” lead author and ORNL microscopist Mary Jane Simpson said. The paper is published in Journal of Physical Chemical Letters.
This map depicts locations of trap states (in purple) in a hybrid perovskite film, with emission and overall photoexcitation distributions measured directly using multimodal ORNL optical imaging techniques.