The localization of wavefunction by disorder makes a conductive material an insulator with vanishing conductivity at zero temperature. A similar outcome is expected for the photocurrent in semiconductor p-n junctions because the photoexcited carriers cannot drift through the device. In contrast, we here show numerically that the bulk photovoltaic effect—the photovoltaic effect in noncentrosymmetric bulk materials—occurs in a noncentrosymmetric, disordered, one-dimensional insulator where all eigenstates are localized. We find this photocurrent remains, even when the energy scale of random potential is larger than the bandwidth. On the other hand, the photocurrent decays exponentially when the excitation is local, i.e., when only a part of the device is illuminated. The photocurrent also vanishes if the relaxation occurs only by contact with the electrodes. Our result implies that the ratio of the photovoltaic current and the direct current by the variable-range hopping increases with decreasing temperature. These results suggest a route to design high-efficiency solar cells and photodetectors.

无序对波函数的定域使导电材料成为在零温度下电导率消失的绝缘体。预期半导体 pn 结中的光电流会产生类似的结果，因为光激发的载流子不能漂移通过器件。相比之下，我们在这里以数值方式展示了体光伏效应——非中心对称体材料中的光伏效应——发生在非中心对称、无序、一维绝缘体中，其中所有本征态都被局部化。我们发现这种光电流仍然存在，即使随机势的能量标度大于带宽。另一方面，当激发是局部的，即只有器件的一部分被照射时，光电流呈指数衰减。如果仅通过与电极接触发生弛豫，光电流也会消失。我们的结果意味着光伏电流和直流电流的比率随着温度的降低而增加。这些结果提出了设计高效太阳能电池和光电探测器的途径。