Halide perovskites are a new class of materials that can be processed at low cost yet exhibit excellent optoelectronic properties – a combination rarely seen in semiconductors. This review highlights their exciting promise for inexpensive and efficient solar photovoltaic technologies. The work highlights the rapid progress in efficiency of solar cells – with efficiencies now rivalling commercial leading technologies such as silicon – and describes the physics of the materials and devices that lend themselves to photovoltaic applications. This work also describes the challenges to realise their true potential as disruptive photovoltaic technologies that could play a key role in decarbonisation in the coming decades, including stabilising long-term operation and furthering understanding of this fascinating class of materials