Optical Absorption and Bandgap Modulation in Diamond-Like Carbon Films for Anti-Reflection

Abstract

Diamond-like carbon (DLC) films were deposited onto glass and silicon substrates utilizing Electron Cyclotron Resonance Chemical Vapor Deposition (ECR-CVD) with an Argon/Acetylene gas mixture. Substrate biases were varied (0V,-55V,-100V) for both nitrogen-doped and undoped films. Optical band gap (Eg) decreased with increasing negative substrate bias specifically from 2.6 eV to 2.2 eV for nitrogen-doped DLC and from 1.6 eV to 1.3 eV for undoped DLC. Nitrogen doping generally results in films with wider band gaps compared to undoped films at equivalent biases to sp hybrid bond formation increasing bias reduces the band gap within each film type. I-V measurements revealed an increase in open-circuit voltage from approximately 0.648 V to a range of 0.678–0.698 V for cells incorporating nitrogen-doped DLC. This improvement is attributed to enhanced corrosion resistance and electrical conductivity suggesting the suitability of nitrogen-doped DLC for photovoltaic applications.