Successfully designing an ideal solar cell requires an understanding of the fundamental physics of photoexcited hot carriers (HCs) and the underlying mechanism of unique photovoltaic performance. Harnessing photoexcited HCs offers the potential to exceed the thermodynamic limit of power conversion efficiency, although major loss channels employing ultrafast thermalization of HCs severely restrict their utilization in conventional bulk-absorber-based solar cells. Spatially confined semiconductors, especially 2D van der Waals (vdW) materials, offer several advantages, such as strong Coulomb interaction, high exciton binding energy, strong carrier–carrier scattering and weak carrier–phonon coupling, resulting in slow HC cooling and restricted loss channels. This Review provides a detailed mechanistic understanding of the HC cooling dynamics in confined vdW layered materials for efficiently utilizing HCs and discusses the role of carrier multiplication in designing a solar cell with the power conversion efficiency exceeding the Shockley–Queisser limit. Additionally, we analyse the major energy loss channels that limit the efficiency of a conventional solar cell, as well as the promises held by the 2D vdW heterostructures for an efficient HC solar cell. Furthermore, we highlight the challenges and opportunities involved in successfully utilizing HCs in practical solar cells with efficiencies beyond the thermodynamic limit.

成功设计理想的太阳能电池需要了解光激发热载流子（HC）的基本物理原理以及独特的光伏性能的基本机制。利用光激发的HC可以提供超过功率转换效率热力学极限的潜力，尽管采用HC超快热化的主要损耗通道严重限制了它们在传统的基于吸收体的太阳能电池中的利用。空间受限的半导体，尤其是2D范德华（vdW）材料具有许多优势，例如强大的库仑相互作用，高激子结合能，强的载流子-载流子散射和弱的载流子-声子耦合，从而导致HC冷却缓慢和损耗通道受限。这篇综述提供了对密闭vdW层状材料中HC冷却动力学的详细机械理解，以有效利用HC，并讨论了载流子倍增在设计功率转换效率超过Shockley-Queisser极限的太阳能电池中的作用。此外，我们分析了限制常规太阳能电池效率的主要能量损失通道，以及2D vdW异质结构对高效HC太阳能电池的承诺。此外，我们重点介绍了在效率超过热力学极限的实际太阳能电池中成功利用HC所涉及的挑战和机遇。