Photovoltaics (PV) is currently at an exciting point in its trajectory. Having recently passed 1 TW of installed capacity world-wide, PV is delivering on its promise to supply the globe with clean energy. However, to meet the growing electricity demand that is required to decarbonize multiple sectors, the growth rate must continue to increase for several more decades. Tandem or multijunction solar cells offer the clearest path to high efficiency and high areal energy density photovoltaic energy conversion, with a great deal of recent effort focused on metal halide perovskite materials. Theoretically and at the laboratory scale, increasing the number of junctions is a simple way to create a record-setting device. Tandem devices can be made using sub-cells out of the same material system with tunable bandgaps (e.g all III-V or all-perovskite tandems) or by combining different material systems into “hybrid tandem” devices (e.g. perovskite/Si tandems). There are multiple approaches to interconnecting the sub-cells in a tandem stack that have different trade-offs in terms of efficiency, cost, and manufacturability. There are also other energy conversion applications, such as the photoelectrochemical production of chemical fuels through the reduction of water or CO₂, or thermophotovoltaic devices that can convert heat to electricity.

To continue advances in tandem and multijunction devices, sustained material research in key and emerging areas along the value chain is vital, including: (i) high efficiency device concepts and architectures for multi-junction solar cells; (ii) development of transparent, carrier-selective contact layers and interfaces; (iii) modeling the performance and energy yield of tandem devices; (iv) advances in packaging and outdoor performance of multijunction devices, and (v) unique reliability challenges of tandem devices, particularly those containing metal halide perovskites. The proposed Multijunction devices for solar energy conversion symposium focuses on these topics but more generally seeks to encompass any materials research with the potential to advance multijunction devices for energy conversion.

III-V perovskites