It is well known that the lattice structure for a crystal can be manipulated through mechanical strain, temperature, an electric field, a magnetic field, and light. In the past, the photostriction commonly occurs at the surface and the bulk photostriction is very small in most semiconductors. Here, the 532 nm laser can excite the excess electron-hole pairs in the surface layer and consequently these carriers diffuse in the millimeter-thick MAPbBr3-xIx crystal and introduce a giant bulk photostriction of 0.17, 0.28, and 0.35% for the 0.5 mm-thick MAPbBr3-xIx single crystals at x = 0, 1, and 2, respectively. Furthermore, the displacement of each crystal linearly increases from hundreds of picometers to several micrometers when the light intensity increases from about 0.2 to 536 mW/cm2. Since both the maximum strain and the displacement accuracy are as good as those of PZT ceramics used in piezoelectric actuators, these crystals can be used in light-driven actuators for precise positioning.
Keywords: bulk photostriction; crystal structure; lead halide perovskites; light-driven actuators; photocarriers; single crystals.