Pyroelectric Energy Harvesting: Materials, Design Strategies, and Multiphysics Mechanisms.

The transition toward a low-carbon, intelligent society requires sustainable power solutions for billions of distributed electronic nodes, including wireless sensor networks (WSNs) and wearable or implantable biomedical electronics. Ubiquitous low-grade waste heat and photothermal energy represent abundant yet underexploited resources, thereby motivating the rapid development of pyroelectric energy harvesters (PyEHs) that directly convert temporal temperature fluctuations into electrical energy. Although progress has been achieved in high figure-of-merit (FOM) pyroelectric materials and in the prototype device demonstrations, PyEHs still face substantial challenges in achieving high energy density, high power density, and effective system integration for practical applications. This review provides a comprehensive overview of waste-heat and photothermal PyEHs, with a focus on revealing performance enhancement methodologies and underlying multiphysics mechanisms. It elucidates generalizable architectures and extracts representative design strategies spanning efficient heat transfer, interface optimization, and hybrid energy conversion mechanisms at the device level, as well as dimensionality effects, composite design and electrode engineering at the material level, in conjunction with energy management circuits. Promising application scenarios, key challenges, and future directions are discussed. This work provides a systematic framework and design guidance to accelerate the development of practical PyEHs for sustainable energy technologies.