Hexagonal manganites, such as $h\text{−}{\mathrm{LuMnO}}_3$, are ferroelectric and have a narrow electronic band gap of $\approx 1.5\mathrm{eV}$. Here we report on the photoresponse of $h\text{−}{\mathrm{LuMnO}}_3$ single crystals. It is found that the short circuit photocurrent density ($J_{\mathrm{sc}}$) and the open circuit voltage ($V_{\mathrm{oc}}$) are dependent on the direction of the polarization plane of a linearly polarized impinging light. Its angular dependence indicates the contribution of bulk photovoltaic effect to the short circuit photocurrent. It is also observed that a switchable drift photocurrent, originating from the depoling field of the ferroelectric and thus tunable $\left(<10\%\right)$ by its polarization direction, also contributes to $J_{\mathrm{sc}}$. Although its presence precludes accurate determination of the bulk photovoltaic tensor elements and Glass coefficients, some bounds can be established. The Glass coefficients are found to be significantly larger than those obtained in ${\mathrm{BiFeO}}_3$. We argue that the smaller band gap of $h\text{−}{\mathrm{LuMnO}}_3$, its distinctive bipyramidal crystal field, and electronic configuration ($3d^4$ vs $3d^5$), account for the difference and suggest a path towards ferroelectrics of higher photoconversion efficiency.

中文翻译：

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六方LuMnO3单晶中的体光伏效应

六方锰矿，如 $H\text{-}{\mathrm{锰酸锂}}_3$, 是铁电体并且具有窄的电子带隙 $\approx 1.5\mathrm{电动汽车}$. 在这里，我们报告了$H\text{-}{\mathrm{锰酸锂}}_3$单晶。发现短路光电流密度 ($J_{\mathrm{sc}}$) 和开路电压 (${伏}_{\mathrm{oc}}$) 取决于线偏振入射光的偏振面方向。它的角度依赖性表明体光伏效应对短路光电流的贡献。还观察到可切换的漂移光电流，源自铁电体的去极场，因此可调谐$\left(<10\%\right)$ 通过其极化方向，也有助于 $J_{\mathrm{sc}}$. 尽管它的存在妨碍了对体光伏张量元素和玻璃系数的准确确定，但可以建立一些界限。发现玻璃系数显着大于在${\mathrm{氧化铋}}_3$. 我们认为较小的带隙$H\text{-}{\mathrm{锰酸锂}}_3$，其独特的双锥晶体场和电子配置（$3d^4$ 对比 $3d^5$)，解释了这种差异，并提出了一条通向具有更高光转换效率的铁电体的途径。