In the modern era marked by rapid technological advancements, ferroelectric materials have gradually emerged as highly promising candidates for a wide range of applications, including ferroelectric memories, sensors, and optoelectronic devices, due to their distinctive polarization characteristics. A common strategy to address the low ferroelectric polarization caused by lattice mismatch between the substrate and ferroelectric film is the insertion of a buffer layer. However, a thicker buffer layer tends to promote dislocation formation, which relaxes epitaxial strain and thereby deteriorates ferroelectric polarization, this mechanism has yet to be systematically explored. In this study, a method is presented that alleviates strain relaxation by modulating interfacial stress through precise control of the buffer layer thickness, thereby enhancing the ferroelectric polarization performance. Here, to reduce the strain between the PbZr_1−xTi_xO₃ (PZT) and substrates, which could induce pronounced lattice mismatch, increased defect density, and consequently reduced ferroelectric performance, a SrRuO₃ (SRO) buffer layer of optimized thickness was inserted between SrTiO₃ (STO) and PZT to mitigate the lattice mismatch. This approach increased the maximum polarization from 126.3 to 142.6 μC/cm², the remanent polarization from 86.52 to 116.03 μC/cm², and enhanced the photocurrent by 2.2 μA. On this basis, the material stack provided robust support for an intelligent traffic-intersection recognition system, achieving a recognition accuracy of 93.23% under diverse weather conditions. The methodology elucidated the fundamental interplay between strain and ferroelectric/photoelectric properties, offering new insights and strategies for the performance optimization of ferroelectric materials.