Electrical and optical properties of p-type codoped ZnO thin films prepared by spin coating technique

• The p-type ZnO thin films synthesized by sol–gel method.
• The average transmittance of the ZnO films is observed 87%.
• A strong UV emission was observed for ZnO thin films.
• Maximum carrier concentration is observed ~6.83×1019 cm−3.

Undoped, doped and codoped ZnO thin films were synthesized on glass substrates using a spin coating technique. Zinc acetate dihydrate, ammonium acetate and aluminum nitrate were used as precursor for zinc, nitrogen and aluminum, respectively. X-ray diffraction shows that the thin films have a hexagonal wurtzite structure for the undoped, doped and co-doped ZnO. The transmittance of the films was above 80% and the band gap of the film varied from 3.20 eV to 3.24 eV for undoped and doped ZnO. An energy band diagram to describe the photoluminescence from the thin films was also constructed. This diagram includes the various defect levels and possible quasi-Fermi levels. A minimum resistivity of 0.0834 Ω-cm was obtained for the N and Al codoped ZnO thin films with p-type carrier conductivity. These ZnO films can be used as a window layer in solar cells and in UV lasers.

Photoluminescence spectra of undoped, doped and co-doped ZnO thin film (b) De-convoluted PL curve of the undoped ZnO (c) A possible band diagram drawn from the fitted data.Figure optionsDownload as PowerPoint slide