Zn doping results in energy level offset and improvement of power conversion efficiency in SnO2 dye-sensitized solar cells

In this work, different percentage Zn-doped SnO2 nanoparticles are synthesized by sol-gel process. The crystalline size and band gap of 3 at% Zn-doped SnO2 nanoparticle are decreased from 27.4 to 13.6 nm and from 3.37 to 3.28 eV, respectively, deduced by the results of XRD and UV-Vis absorption spectroscopy compared with un-doped SnO2. Zn-doped SnO2 film as a photoanode for dye-sensitized solar cells (DSCs) was characterized and investigated by ultraviolet photoelectron spectroscopy (UPS) and electrochemical impedance spectroscopy (EIS). Conduction band (CB) of the Zn-doped SnO2 is adjusted from - 4.78 to - 4.64 eV via 3 at% Zn concentrations. By adjusting the Zn concentrations, energy offset between the SnO2 and dye is reduced, which accelerates the charge transfer. The cells were estimated once at the interval of one day within 18 days after fabrication. Power conversion efficiency (PCE) of 3 at% Zn-doped SnO2 DSCs increases step by step and achieves 5.18% as the cell is tested after 5 days. This slowly increasing phenomenon of PCE in pure and Zn-doped SnO2 DSCs differs from that of TiO2 and ZnO DSCs. This phenomenon is a different direction for DSCs, revealing the nature of this phenomenon and possibly a breakthrough in efficiency.

Automated summary

Different percentage Zn-doped SnO2 nanoparticles were synthesized using a sol-gel process. The addition of Zn reduced the crystalline size and band gap of the SnO2 nanoparticles, leading to improved charge transfer and increased power conversion efficiency in dye-sensitized solar cells.