Silicon solar cells enjoy promising prospects in the photovoltaic industry and have attracted considerable attention. Especially silicon solar cells with tunnel oxide passivating contact (TOPCon) structures are rising as a competitive photovoltaic technology, due to their ultra-high power conversion efficiency (PCE), cost advantage, and mass production capability.

Prof. YE Jichun’s team from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), along with Prof. YU Xuegong’s team from Zhejiang University, has developed a highly passivated TOPCon bottom cell, achieving perovskite/silicon tandem solar cells (TSCs) with high open-circuit voltages (V_OCs) and excellent efficiencies.

The study was published in Nature Communications.

Numerous defects at the fragile silicon oxide/c-Si interface and the weak field-effect passivation on textured substrates reduce the V_OCs of current TOPCon silicon solar cells, thus limiting their application for high-performance perovskite/silicon TSCs.

In this study, researchers prepared highly passivated p-type TOPCon structures and double-sided TOPCon bottom cells on industrial textured wafers via industry-compatible fabrication methods, including ambient-pressure thermal oxidation and in situ plasma-enhanced chemical vapor deposition.

Through optimizing the oxidation conditions, boron in-diffusion, and aluminum oxide hydrogenation, the passivation quality of the as-prepared p-type TOPCon structures has been significantly improved.

Compared with its conventional counterparts, the sample with the optimized p-type TOPCon structures shows a superior implied V_OC(iV_OC) of 715mV.

Besides, the V_OC of completed double-sided textured TOPCon bottom cells has risen to 710mV from 690mV, leading the industry of TOPCon bottom cells.

Integrating the as-prepared TOPCon bottom cells with perovskite top cells, the perovskite/Si TSCs achieve an impressive V_OC of 1.9 V and PCE of 28.2% (certified 27.3%), which is at the top-ranking level for 1 cm² n-i-p type monolithic perovskite/silicon TSCs currently.

This work shows the broad application potential of highly passivated TOPCon bottom cells for tandem devices and sheds light on their future commercialization.

Fig. The structure and performance of tandem devices with highly passivated TOPCon bottom cells (Image by NIMTE)