The evolution of this device – relatively slow in the past – has accelerated in recent years, posing now new challenges and opening exciting opportunities. Its recent success as an economically viable source of electricity is founded on a simple optoelectronic device, the crystalline silicon solar cell. Broader context Photovoltaic solar energy offers humankind a useful instrument to build a globally prosperous, sustainable, and environmentally friendly society. Last, it gives an up-to-date summary of promising recent pathways for further efficiency improvements and cost reduction employing novel carrier-selective passivating contact schemes, as well as tandem multi-junction architectures, in particular those that combine silicon absorbers with organic–inorganic perovskite materials. Next it analyzes two archetypal high-efficiency device architectures – the interdigitated back-contact silicon cell and the silicon heterojunction cell – both of which have demonstrated power conversion efficiencies greater than 25%. First, it discusses key factors responsible for the success of the classic dopant-diffused silicon homojunction solar cell. This article reviews the dynamic field of crystalline silicon photovoltaics from a device-engineering perspective. With a global market share of about 90%, crystalline silicon is by far the most important photovoltaic technology today.