Triple-junction solar cells with improved carrier and photon management

Perovskite-silicon triple-junction photovoltaics offer efficiency gains beyond dual-junction devices but at the expense of added complexity¹. Here we address two key bottlenecks in perovskite-silicon-based triple-junction solar cells: reduced open-circuit voltage (V_OC) in the wide-bandgap (WBG) top cell and limited photocurrent generation in the middle cell^1,2. A non-volatile additive, 4-hydroxybenzylamine (HBA), regulates WBG perovskite crystallization and passivates defects, promoting oriented growth and suppressing non-radiative recombination. Together with improved energy-level alignment, this yields V_OCs of up to 1.405 V and enhanced stability. To overcome the current limitations in the middle cell, a three-step deposition strategy enables the formation of thick, low-bandgap perovskite absorbers while preserving microstructural integrity and enhancing electron extraction. Also, low-refractive-index SiO_x-nanoparticles (SiO_x-np) that accumulate in the front valleys of the textured silicon bottom cell act as an optical middle reflector, enhancing light absorption in the middle cell. These advances are then combined in 1-cm² perovskite-perovskite-silicon devices, achieving a certified efficiency of 30.02%.