Protective buffer layer engineering for sputter-resistant transparent perovskite solar cells with improved transmission and efficiency

Abstract

The identification of an optimal sputter buffer layer with higher transmission and conductivity remains a critical challenge in the fabrication of transparent perovskite solar cells (T-PSCs). It plays a vital role in protecting the underlying layers during highly energetic radio frequency (RF) magnetron sputtering, a process known to induce surface damage, while facilitating excellent light transmission. This study explores five metal oxides (MOs) – Y₂O₃, SnO₂, WO₃, MoO₃, and Pr₆O₁₁ – as potential sputtered buffer layers for the fabrication of efficient T-PSCs applicable for both substrate and superstrate configurations in tandem solar cells. The d-block metal oxides exhibited the highest optical average transmission (T_av) values of ∼86% and ∼88% across the visible and near-infrared (NIR) ranges under substrate and superstrate illumination conditions, respectively. Moreover, WO₃ facilitates an improved defect-free electronic coupling at the spiro-MeOTAD and IZO interface. As a result, the champion T-PSCs having E_g ∼1.6 eV and an active area of 17.5 mm² achieved the highest power conversion efficiency (PCE) of 19% with an optimal buffer thickness, which effectively balances protection and low contact resistance. Concurrently, WO₃-based device shows an excellent transmission of ∼42% in the wavelength range of 300–1200 nm and ∼77% in the NIR range (800–1200 nm), which will be suitable for tandem applications. Additionally, the average transmission of ∼26% and ∼11% in the wavelength range of 300–900 nm and 390–780 nm, respectively, will be applicable for building-integrated PV (BIPV) applications. By coupling with 23% efficient monocrystalline passivated emitter rear contact (PERC) Si solar cells, a combined efficiency of 26.71% is achieved in four-terminal (4T) tandem configurations. Stability tests showed that the champion devices retained 90% efficiency after ∼90 days under inert conditions and 80% under harsh thermal and moisture exposure for ∼45 days. These results highlight the critical role of the buffer layer in advancing T-PSCs, offering improved performance and stability for scalable photovoltaic technologies.