Photocurrent enhancement by Ni²⁺ and Zn²⁺ ion doped in SnO₂ nanoparticles in highly porous dye-sensitized solar cells

Searching on alternative photoanode materials for dye-sensitized solar cells (DSSCs) evidenced that rare works have been reported on studying Ni ²⁺ and Zn²⁺ doped SnO₂ nanoparticles. Mostly efficient DSSCs with perfect long-term stability were fabricated based on tin (IV) oxide (SnO₂) nanocrystals doped with different metals ions. The co-precipitation technique was applied to prepare M-doped SnO₂ nanoparticles. Moreover, the obtained powders were investigated using XRD, HRTEM, BET specific surface area (S_BET) and UV-vis spectroscopy. In addition, an economic way to prepare semiconducting pastes for photoanodes was devised. The photovoltaic performance of dye-sensitized solar cells based on undoped and Ni²⁺ and Zn²⁺ doped SnO₂ photoanodes was investigated. Zn and Ni doped SnO₂, respectively, have a high power conversion efficiency of up to 4.2% and 3.6%, higher than that of undoped SnO₂ which is 3.2% and the reason for this difference is that the Zn and Ni-doped films exhibit an elevated electron Fermi level, which may enhance band bending to lower the density of empty trap states. On account of these doping metals, the consequent DSSCs can alleviate the decay of light to electric energy conversion efficiency due to light intensity reduction. The enhanced transport of photogenerated electrons as a result of the trap density minimization is responsible for the high photovoltaic performance.