Preparation Of BZO Thin Films For Heterojunction Solar Cells By MOCVD

The traditional transparent conductive electrodes are mainly the ITO or FTO, which has the disadvantage of rare raw material, high price and toxic. It seriously restricts the development of solar cells. Zinc Oxide has the electrical and optical properties comparable to the ITO or FTO, and has the low price which has wider applications. The incorporation of impurities such as B, Al, Ga, In and other impurities can improve the electrical properties of ZnO films. Since the Ga and In is rare and toxic, and Al doped ZnO thin films has poor stability in the humid environment, the research of B doped ZnO thin films has important practical significance.We have fabricated the BZO thin films by MOCVD. During the prepared process, we have studied the surface morphology, lattice structure and photoelectric properties and of BZO films with different B content and substrate temperature. Finally we got the optimized parameters and found that the film has the smallest resistivity of 1.1x10-3?cm with B2H6 flow rate of 10 sccm and the substrate temperature of 170 oC.We have also studied the surface morphology and photoelectric properties of BZO thin films with different thickness. By applying the BZO thin films to the bifacial heterojunction solar cells, we have synthetically analyses the performance of the cells and got the optimized parameter of thickness. From the experiment, we got that the highest conversion efficiency was 17.8% with the thickness of 829 nm, meanwhile, the open circuit voltage(Voc) was 0.631 V, short-circuit current(Jsc) was 41.79mA/cm2 and the fill factor(FF) was 0.676.Finally, we have modified the surface morphology and improved the light trapping structure by fabricated the double layer BZO thin films and the Ar plasma etching. We found that the double layer BZO have both large and small size of surface grains which could enhance the scatting ability of both long and short wavelength light, thereby increase the absorption of different wavelength light of the solar cells. The conversionefficiency improved from 17.8% to 18.6%; After 50 mins etch of Ar plasma, the surface morphology of the BZO thin films changed from the inverted V type sharp pyramid into U shaped and the grain size become differentiation, both the transmittance and the scatter ability enhanced. The conversion efficiency of the solar cells improved from 17.8% of non-etched to 18.9%.