Samsung Advanced Institute of Technology

Metal halide perovskite solar cells have been considered as one of the most promising next-generation energy harvesters for the past decade by showing remarkably rapid improvement of power conversion efficiency (PCE) in the field of photovoltaics. However, the energy harvesters based on the solar energy source have intrinsic environmental limitations, which can be obstacles for various indoor applications. A feasible solution to resolve the limitations is to add non-solar energy harvesting functions to the solar energy harvesters. Piezoelectricity is a representative non-solar energy harvesting mechanism based on the energy conversion from the mechanical energy source to electricity. Here, we investigate the piezoelectric properties of two types of metal halide perovskite solar cells, the 3 dimensional (3D) and the 3D/2D structure, showing the PCE of ~21.1 ％ ~23.2 ％, respectively. The piezoresponse force microscopy (PFM) and the synchrotron-based X-ray diffraction (XRD) demonstrate that both types of PSC samples have piezoelectricity. Remarkably, the perovskite solar cells of the 3D/2D heterostructure show considerably higher piezoelectric amplitude than those of the 3D based devices. Based on the deep level transient spectroscopy (DLTS), it is revealed that the enhancement in the piezoelectricity of 3D/2D structure is originated from the increasing PbBr defect states. This study unravelled the role of defects in the piezoelectricity of metal halide perovskite solar cells and provided the direction to develop the multi-function energy harvesters based on the perovskite solar cells.