Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
Science. 2018 May 25;360(6391):904-907. doi: 10.1126/science.aan3256. Epub 2018 Apr 19.
It is highly desirable to discover photovoltaic mechanisms that enable enhanced efficiency of solar cells. Here we report that the bulk photovoltaic effect, which is free from the thermodynamic Shockley-Queisser limit but usually manifested only in noncentrosymmetric (piezoelectric or ferroelectric) materials, can be realized in any semiconductor, including silicon, by mediation of flexoelectric effect. We used either an atomic force microscope or a micrometer-scale indentation system to introduce strain gradients, thus creating very large photovoltaic currents from centrosymmetric single crystals of strontium titanate, titanium dioxide, and silicon. This strain gradient-induced bulk photovoltaic effect, which we call the flexo-photovoltaic effect, functions in the absence of a p-n junction. This finding may extend present solar cell technologies by boosting the solar energy conversion efficiency from a wide pool of established semiconductors.
发现能够提高太阳能电池效率的光伏机制是非常理想的。在这里，我们报告说，体光伏效应不受热力学 Shockley-Queisser 限制的限制，但通常仅在非中心对称（压电或铁电）材料中表现出来，通过介电体弹性效应，可以在任何半导体中实现，包括硅。我们使用原子力显微镜或微米级压痕系统引入应变梯度，从而从钙钛矿、二氧化钛和硅的中心对称单晶中产生非常大的光伏电流。我们称这种应变梯度诱导的体光伏效应为介电体弹性光伏效应，它在没有 p-n 结的情况下起作用。这一发现可能会通过提高现有半导体的太阳能转换效率，从而扩展现有的太阳能电池技术。
