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The origins of parasitic heating for photovoltaic (PV) technologies based on silicon, perovskites, and their combination in monolithic tandems are investigated. To quantify heating losses, the cooling score (CS) as a new simple metric, representing the percentage of incident solar irradiance not contributing to module heating is introduced. This is a function of both the optical structure and power conversion efficiency (PCE) of the PV modules and allows a fair comparison between different technologies under identical performance‐evaluation scenarios. Silicon single‐junction devices have the lowest CS due to their low bandgap (causing significant carrier thermalization losses) and their use of light‐trapping structures to increase their PCE which also undesirably increases parasitic absorption of sub‐bandgap photons. Conversely, perovskite single‐junction devices show the highest CS in all studied performance‐evaluation scenarios thanks to their wider bandgap and high absorption coefficient, enabling absorption of all solar photons that may contribute to the photocurrent without requiring light‐trapping structures. While perovskite/silicon tandems minimize thermalization losses, they also usually employ light‐trapping structures in their bottom cell to increase their PCE, which lowers their CS. Through simulation and outdoor experiments, it is demonstrated that an efficient module‐cooling environment may significantly suppress the detrimental effects associated with a low CS. [ABSTRACT FROM AUTHOR]

Over the past few years, perovskite solar cells have arisen as a technology to potentially side with mainstream silicon photovoltaics (PVs) to help drive the transition towards renewable sources of energy. The coupling of perovskites with silicon in a tandem configuration may accelerate this development due to the remarkably high power conversion efficiencies possible with such devices. However, most of the perovskite/silicon tandem achievements so far have been confined to the lab environment, with only a few reported tests under outdoor conditions, using packaged devices. Nevertheless, one of the major challenges for perovskite/silicon tandem technologies, in addition to scale‐up, lies in the cell‐to‐module (CTM) translation, which for the perovskite/silicon tandem concept is complicated by perovskite‐imposed constrains such as a low‐temperature resilience, imposing challenges regarding tabbing and lamination, as well as a high sensitivity to moisture ingress, mandating the search for adequate encapsulation materials and methods. Herein, these challenges are described and assessed in depth and a perspective on future directions toward module design, tailored for perovskite/silicon tandem PVs is given, combining high performance with excellent durability. The discussion also holds relevance for all‐perovskite and other emerging PV technologies seeking market entry. [ABSTRACT FROM AUTHOR]