Controllable Simultaneous Bifacial Cu‐Plating for High‐Efficiency Crystalline Silicon Solar Cells

Bifacial (BF) copper‐plated crystalline silicon solar cell is an attractive topic to concurrently reduce silver consumption and maintain good device performance. However, it is still challenging to realize a high aspect ratio (AR) of the metal fingers. Herein, a new type of hybrid‐shaped Cu finger is electromagnetically fabricated in a BF plating process. Cyclic voltammetry is employed to disclose the electrochemical behaviors of cupric ions in monofacial and simultaneous BF Cu‐plating processes, such that the controllability of the plating process could be assessed. The optimal hybrid Cu finger is composed of a rectangular bottom part and a round top part, such that an utmost effective AR value of 1.73 is reached. In BF Cu‐plating, two sub‐three‐electrode electrochemical cells are employed to realize equal metal finger heights on both sides of the wafer. Compared to our low thermal‐budget screen‐printing metallization, the Cu‐plated silicon heterojunction devices show both optical and electrical advantages (based on lab‐scale tests). The champion BF Cu‐plated device shows a front‐side efficiency of 22.1% and a bifaciality factor of 0.99.