Cu‐Implanted MXene/TiO₂ Photoanodes for Efficient Quantum Dot‐Sensitized Solar Cells

Noble metal‐doped TiO₂‐based photoanode for quantum dot‐sensitized solar cells (QDSSCs) has gained significant importance in enhancing performance by increasing the light absorption and subsequently minimizing the number of recombinations due to the formation of new charge trap states. In this work, Cu ions are implanted in MXene/TiO₂‐based photoanode at different fluence rates (5 × 10¹², 5 × 10¹³, 5 × 10¹⁴, and 5 × 10¹⁵ ions cm⁻²). The X‐ray photoelectron spectroscopy investigations reveal the doping mechanism as at lower fluence, Cu⁺ ions are present, but as the fluence increased the Cu²⁺ ions dominate. The field emission scanning electron microscopy and energy‐dispersive X‐ray analysis are used to find the surface morphology and the elemental composition of the implanted samples. The implantation of Cu ions creates new impurity states between the energy bands, thereby enhancing light absorption capabilities and suppressing charge recombinations of the photoanode, which is confirmed by UV‐Vis and photoluminescence spectroscopy. Afterward, Cu‐implanted photoanodes are employed to fabricate QDSSC devices, and the QDSSC based on photoanode implanted at 5 × 10¹⁴ ions cm⁻² fluence (Cu_3) demonstrates the highest power conversion efficiency of 3.86%, which is 34.9% higher than pristine unimplanted photoanode. This enhancement is attributed to the inhibition of the charge recombinations at the photoanode/electrolyte interface and enhanced light harvesting capability of the photoanode.