Fundamental and technical advances in bulk photovoltaics of 2D van der Waals materials.

2D van der Waals (vdW) materials with exceptional electronic and optical properties have emerged as a hotspot of materials science research. Over the last few years, substantial growth has been observed in the engineering of these materials for the bulk photovoltaic effect (BPVE). BPVE is the conversion of electricity from light via an entirely distinct mechanism from the p-n junction photovoltaic device. The tunable crystal structures of 2D vdW materials, their ability to maintain clean interfaces, and the ease of forming heterostructures and heterojunctions facilitate the manipulation of crystal symmetry, electronic polarization, light-matter interactions, thereby providing an efficient platform for engineering the BPVE. Herein, we present a critical discussion of the fundamentals of engineering the BPVE using different material systems and innovative strategies based on previous scientific reports. The key challenges that can hinder device efficiency are also covered. The potential for a next-generation, self-powered, energy-efficient, flexible, and lightweight device utilizing the BPVE of 2D vdW materials is highlighted in this article.