A research team, led by the Chinese Academy of Sciences (CAS), has developed a novel chemical polishing approach to improve the performance of perovskite/silicon tandem solar cells (PVSK/Si TSCs), achieving a power conversion efficiency (PCE) increase from 30.04% to 31.83%.
In conventional tandem devices fabricated using spin-coating techniques, the bottom crystalline silicon layer typically features sub-micron pyramid (SMP) textures. These pyramid structures, though essential for light trapping, produce deep V-shaped grooves between adjacent pyramids, which hinder substrate wettability and raise surface roughness. Such morphologies make it difficult to deposit uniform, defect-free perovskite films, ultimately limiting device efficiency. To address these issues, the team applied an isotropic etching-based chemical polishing process to smooth the V-shaped regions of the SMP texture.
By subtly modifying the surface shape without sacrificing the light-trapping advantage, the method enhances the interfacial passivation between crystalline and amorphous silicon, while simultaneously improving surface wettability. The refined texture promotes better adhesion and more uniform coverage of the perovskite layer.
At the microstructural level, the reduced roughness helps mitigate pore formation and lattice strain during perovskite crystallization, leading to higher film uniformity and improved crystalline quality. These changes translate directly into stronger interfacial contact, reduced recombination losses, and improved electrical transport properties within the tandem stack.
Performance testing of the optimized devices revealed simultaneous improvements in open-circuit voltage and short-circuit current density, along with negligible hysteresis effects - indications of excellent interfacial stability and efficient charge extraction. This work highlights the important role of the silicon bottom cell’s surface engineering in defining overall tandem performance, and opens new pathways for designing high-efficiency photovoltaic architectures through careful control of interfacial texture and chemistry.
