De-coupling of optical and electrical properties in front TCO using the bilayer concept for thin-film solar cells

This study investigates the transparent conductive oxides (TCOs) as front contact for thin-film solar cell applications by developing a bilayer design that decouples the optical and electrical functionalities. The bilayer front contact structure combines hydrogenated indium oxide (IOH) and non-intentionally doped zinc oxide (ZnO) materials. This design achieves enhanced optoelectrical properties with a mobility of 120 cm 2 /Vs and a carrier density of 1.97·10 19 cm -3 . Notably, the bilayer outperforms the expected average of its constituent layers in both transparency and conductivity, reflecting the benefits of optimized layer architecture. When integrated as the front electrode in a hydrogenated nanocrystalline silicon (nc-Si:H) solar cell, the IOH/ZnO bilayer yields a fill factor of 64.56 % and a power conversion efficiency of 7.85 %. When using an ITO front contact, the nc-Si:H solar cell reveals a fill factor of 56.27 % and an efficiency of 6.80 %. By successfully decoupling optical and electrical properties, the optimized IOH/ZnO bilayer offers a significant advancement over single-layer TCO configurations, presenting an innovative pathway for enhanced performance in thin-film solar cell technology. • Optical and electrical properties of front contact can be decoupled using the bilayer concept. • Undoped zinc oxide ensures transparency, while hydrogenated indium oxide boosts conductivity. • The bilayer geometry facilitates efficient lateral transport of charge carriers. • Solar cell performance highlights the impact of the bilayer design as a front contact.