Performance Constraints of All‐Perovskite Tandem Solar Cells in Low‐Intensity, Low‐Temperature Environments

Abstract All‐perovskite tandem solar cells (2J‐PSCs) reach the highest power‐to‐weight ratios, making them promising candidates for space applications. To determine their potential for future deep space missions, this study assesses the performance of 2J‐PSCs under low‐intensity and low‐temperature (LILT) conditions, akin to those found near Saturn, the Asteroid belt, or in eclipse. Temperature‐dependent current density‐voltage ( J – V ) measurements under varying solar intensities (AM0, 0.1 AM0, 0.01 AM0) reveal that the 2J‐PSCs, comprising 1.80 eV high‐bandgap and 1.27 eV low‐bandgap perovskites, exhibit significant efficiency losses at lower temperatures and low light levels. In contrast, 1.54 eV single‐junction PSCs (1J‐PSCs) exhibit resilient performance, maintaining or even increasing their power conversion efficiency at low temperatures. The main performance problem of the 2J‐PSCs is then identified as a demixing of the 1.80 eV perovskite due to its high Br ratio at temperatures below 250 K. This demixing at low temperatures leads to a significant increase in ion‐induced performance losses as well as current imbalances between the two subcells in the monolithic tandem. Together, this causes severe S‐shapes in solar cell operation and impedes the operation of the monolithic interconnected tandem solar cells. Notably, these limitations vanish upon heating, leading to a recovery of performance.