Triple-junction solar cells with improved carrier and photon management

Abstract

Perovskite-silicon triple-junction photovoltaics offer efficiency gains beyond dual-junction devices, but at the expense of added complexity (1). Here, we address two key bottlenecks in perovskite-silicon-based triple-junction solar cells: reduced open-circuit voltage in the wide-bandgap top-cell and limited photocurrent generation in the middle-cell (1, 2). A non-volatile additive, 4-hydroxybenzylamine, regulates wide-bandgap perovskite crystallization and passivates defects, promoting oriented growth and suppressing non-radiative recombination. Together with improved energy-level alignment, this yields open-circuit voltages 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. In addition, low-refractive-index SiO_x nanoparticles 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%.