Ultrawide-bandgap (UWBG) perovskites are essential for monolithic all-perovskite triple-junction solar cells. However, their performance is limited by severe surface wrinkling, halide heterogeneity and large open-circuit voltage deficits originating from high Br–I ratios. Here we develop a surface reconstruction and halide homogenization strategy that simultaneously regulates crystallization and eliminates stress-induced morphological disorder in 2.0-eV bandgap perovskites. Through synergistic solvent and additive engineering, involving solvent-induced surface reconstruction and transient Cl− incorporation from oleylammonium chloride, surface wrinkling is suppressed, and Br/I crystallization is synchronized with promoted homogeneous halide distribution. The resulting UWBG perovskite films show uniform surface potential, suppressed non-radiative recombination, improved carrier mobility and an open-circuit voltage of 1.46 V. Integrating this UWBG subcell with optimized 1.6- and 1.22-eV absorbers yields monolithic all-perovskite triple-junction solar cells with 30.1% power conversion efficiency (certified 29.3%) and robust operational stability, providing a promising route towards >35% efficient all-perovskite multijunction photovoltaics. Ultrawide-bandgap perovskites suffer from heterogeneities during crystallization. Zhang et al. use solvent and additive engineering to smooth the process for 2.0-eV bandgap perovskites, enabling 30.1% efficiency in all-perovskite triple-junction solar cells.
Solid electrolytes have long been treated as materials that block electronic conduction while enabling fast lithium-ion transport. Two studies now show that residual electronic conductivity can drive self-discharge in solid-state batteries at open circuit, particularly in thin practical cells, and identify the limits needed to ensure long shelf life.
Rechargeable lithium–sulfur batteries offer a promising route to high-energy storage using abundant sulfur, but their energy density is constrained by low operating voltage, sluggish redox kinetics and polysulfide shuttling. Raising sulfur to higher oxidation states could increase cell voltage, yet reversible high-valence sulfur chemistry in lithium batteries remains difficult because chloride species bind Li+ and halogen-mediated reactions consume electrolyte. Here we show that a free-chloride-rich ionic liquid electrolyte enables a Li||S2Cl2 chemistry that addresses these limitations by reversibly converting Li2S to S2Cl2 through a three-electron sulfur redox process. The electrolyte functions as an ionic mediator with only a minor capacity contribution. This chemistry increases the average operating voltage from 2.05 to 2.54 V at 25 °C and 0.2C, raises sulfur-specific capacity by 58% and delivers an electrode-level specific energy above 1,700 Wh kg−1 with cycling over 100 cycles. Rechargeable Li–S batteries offer high energy density but are limited by low voltage, sluggish kinetics and polysulfide shuttling. Here the authors report a chlorine-mediated Li||S2Cl2 chemistry enabling reversible three-electron sulfur redox with increased voltage and capacity.
Ultrawide-bandgap perovskites are essential for all-perovskite triple-junction solar cells, yet their high bromide content causes surface wrinkling and halide disorder, limiting the performance. A surface reconstruction and halide homogenization strategy now enables a certified efficiency of 29.3% in all-perovskite triple-junction devices.
