Lanthanum (La)-doped ZnO nanofilms were prepared by facile dip-coating method. The surface morphologies and crystallinity of the prepared films were examined by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) pattern, respectively. The optical properties were studied by diffuse reflectance spectra measured by UV-vis spectrophotometer and the optical band gap values were determined by differential reflectance and Kubelka-Munk theory. To investigate the electrical properties, the prepared undoped and La-doped ZnO nanofilms were examined by Hall measurement system under 0.55T magnetic flux at room temperature. The obtained results have revealed that the incorporation of La in ZnO causes a decrease in particle size and crystallinity whereas it leads to an increase in the optical band gap, which can be expressed by the Burstein-Moss effect. The electrical characterization of heterostructure diode consisting of n-ZnO:La and p-Si was investigated by current-voltage (I-V) characteristics in dark and under illumination. After 100 mWcm(-2) the illumination, an increase of almost two orders of magnitude in the reverse current of the diode was observed. This indicate that the n-ZnO:La/p-Si heterostructure diode can be used as a sensor for optoelectronic applications.