Topology and texture controlled ZnO thin film electrodeposition for superior solar cell efficiency

• Developed a low cost electrochemical deposition process for high quality ZnO film.
• The crystal orientation, surface morphology and film texture can be controlled.
• Achieved superior light trapping using the optimized textured ZnO films.
• Attained high quantum efficiency (current density) and solar cell efficiencies.

It is known that the properly textured ZnO film can increase light-scattering and therefore improves light-trapping inside the solar cells, resulting in increased Jsc value and consequently solar cell efficiency. Using a low cost solution-based electrochemical deposition, we have developed a ZnO thin film deposition process that offers fine-control of crystal orientation, surface morphology and texture by tuning an additive concentration. Using the optimized textured ZnO films, we have achieved superior light trapping performance especially in long wavelength spectrum (λ>610 nm) comparing to the vacuum sputtered ZnO. Using single junction a-SiGe:H and multi-junction a-Si:H/a-SiGe:H/a-SiGe:H thin film solar cells, high quantum efficiency (current density) and solar cell efficiencies are attained. It demonstrates that the low cost electrochemical ZnO deposition is an effective method to prepare high quality ZnO film for solar cells.