Abstract:
Chalcogenide-based thin-film photovoltaics (PVs) like CdTe and Cu(In,Ga)Se₂ (CIGSe) surpass 20% efficiency but face scalability issues due to toxicity and element scarcity. Kesterite-based Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells offer a non-toxic, earth-abundant alternative with potential efficiencies over 30%; however, their best efficiency remains around 15.1% (IOP, CAS, China), limited by voltage deficits from defects, band alignment, and interface losses.
Our research addresses these challenges through strategies including metal precursor inter-diffusion enhancement, Ge doping to suppress antisite defects, MoO₃ nanolayers to prevent detrimental interface reactions, and alkali fluoride layers as electron-selective contacts. We also explored CdS/CZTSSe junction interface engineering by optimizing soft-baking temperature, significantly reducing defects and recombination, increasing efficiency from 4.88% to 8.48%. Ag-ion incorporation effectively reduced intrinsic defects in CZTSe, achieving a notable efficiency of 10.2% and improved open-circuit voltage.
Furthermore, our hydrogen-assisted selenization (HAS) process reduced harmful anion vacancies (Vₛ, Vₛₑ), enhanced carrier collection, and lowered activation energy from 184 to 145 meV. Synchrotron-based X-ray nanoprobe analysis directly linked compositional uniformity with enhanced photovoltaic performance. Overall, our comprehensive structural, defect, and interface engineering approach significantly advances the practical potential of kesterite photovoltaics.