Room‐Temperature Atomic Layer Deposited Titanium Oxide as Electron‐Selective Passivating Layer for Dopant‐Free Crystalline Silicon Solar Cells

Owing to its small conduction band offset and excellent passivation of n‐type silicon (n‐Si) surfaces, titanium oxide (TiO x ) has emerged as a promising electron‐selective passivating material for dopant‐free silicon solar cells. However, high‐performance TiO x films usually require fabrication or postannealing at temperatures >200°C, which exceeds the thermal budget for commercial silicon heterojunction (SHJ) solar cell production. Herein, we report a room‐temperature atomic layer deposition (ALD) process to prepare efficient TiOx electron‐selective passivating layers on n‐Si substrates. The as‐deposited TiO x films achieve a maximum minority carrier lifetime of 2.3 ms and a low work function of 3.88 eV, enabling ohmic contact with n‐Si and a minimum specific contact resistivity of 25 mΩ·cm². Integrating this full‐area dopant‐free back contact into silicon solar cells, this contact increased the cell efficiency by 1.6%pt, rising from 15.19% to 16.79%. Furthermore, after 200°C annealing, the specific contact resistivity and minority carrier lifetime retain 1.88 and 0.98 times their initial values, respectively, demonstrating the excellent low‐temperature compatibility of the ALD‐TiOx films for commercial SHJ applications.