太阳能电池中石墨烯的400倍提升
物理与天文学系的Hui Zhao教授和研究生Samuel Lane将石墨烯层与另外两个原子层连接起来，二硫化钼和二硫化钨，将石墨烯中激发电子的寿命延长了几百次。这将有助于以高效率加快超薄和柔性太阳能电池的发展。
兴奋的电ns move in graphene at a speed of 1/30 of the speed of light, much faster than other materials, but with an ultrashort lifetime of 1ps. One of the biggest challenges to achieving high efficiency in solar cells with graphene is that the liberated electrons lose energy quickly and become immobile.
“The number of electrons that can contribute to the current is determined by the average time they can stay mobile after they are liberated by light,” said Prof Zhao. “In graphene, an electron stays free for only one picosecond. This is too short for accumulating a large number of mobile electrons. This is an intrinsic property of graphene and has been a big limiting factor for applying this material in photovoltaic or photo-sensing devices. Although electrons in graphene can become mobile by light excitation and can move quickly, they only stay mobile too short a time to contribute to electricity.”
带有单层摩西的三层材料2, WS2and graphene on top of each other tackles that challenge.
“When light strikes the sample, some of the electrons in MoSe2are liberated. They are allowed to go across the WS2-layer to the graphene. Once in graphene, they have no choice but to stay mobile and hence contribute to electric currents,” he said.
To test out the material the researchers used an ultrashort laser pulse (0.1 picosecond) to liberate some of the electrons in MoSe2. By using another ultrashort laser pulse, they were able to monitor these electrons as they move to graphene. They found that these electrons move through the WS2layer in about 0.5 picosecond on average and then stay mobile for about 400 ps in the graphene, a 400-fold improvement than a single layer of graphene, which they also measured in the same study.
The researchers also confirm the electrons tunnel back into the MoSe2layer, and using different intermediate layers can control the tunnelling time for various applications.
Related stories:
