Scientists at Los Alamos National Laboratory and their research partners are creating innovative 2-D layered hybrid perovskites that allow greater freedom in designing and fabricating efficient optoelectronic devices. Credit: Los Alamos National Laboratory
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating innovative 2D layered hybrid perovskites that allow greater freedom in designing and fabricating efficient optoelectronic devices. Industrial and consumer applications could include low cost solar cells, LEDs, laser diodes, detectors, and other nano-optoelectronic devices “Our material is a layered compound, meaning it is a stack of 2D layers of perovskites with nanometer thickness, and 2D perovskite layers are separated by thin organic layers,” said Jean-Christophe Blancon. “This work could overturn conventional wisdom on the limitations of device designs based on layered perovskites.”
The 2D, near-single-crystalline “Ruddlesden-Popper” thin films have an out-of-plane orientation so that uninhibited charge transport occurs through the perovskite layers in planar devices. At the edges of the perovskite layers, the new research discovered “layer-edge-states,” which are key to both high efficiency of solar cells (>12%) and high fluorescence efficiency (a few 10s of %) for LEDs. The spontaneous conversion of excitons (bound electron-hole pairs) to free carriers via these layer-edge states appears to be the key to improving photovoltaic and light-emitting thin-film layered materials.
The team investigated both photophysical and optoelectronic properties of phase-pure homogenous 2D perovskites. They were able to show that thin films have an intrinsic mechanism for dissociation of the strongly bound electron-hole pairs (excitons) to long-lived free-carriers provided by lower energy states at the edges of the layered perovskites.
Moreover, once carriers are trapped in these edge states, they remain protected and do not lose their energy via non-radiative processes. They can contribute to photocurrent in a photovoltaic (PV) device or radiatively recombine efficiently for light-emission applications. “These materials are quantum hybrid materials, possessing physical properties of both organic semiconductors and inorganic semiconducting quantum wells. We are just beginning to understand the interplay of the organic and inorganic components in 2D perovskites and this result underpins how unique properties can arise from competing physical properties,” said Jared Crochet of the Physical Chemistry and Applied Spectroscopy group at Los Alamos.
http://www.lanl.gov/discover/news-release-archive/2017/March/03.09-perovskite-edges.php
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