DescriptionMGxZN1-xO, which is formed by alloying ZnO with MgO, has been developed as a promising window layer in chalcopyrite thin film solar cells and hybrid polymer solar cells for enhanced open-circuit voltage and solar conversion efficiency because of its bandgap tunability. The surface morphology of MgxZn1-xO layers in those photovoltaic applications plays important roles on the performances of solar cells. Two-dimensional (2-D) dense and smooth film is preferred in the inorganic p-n junction solar cells while one-dimensional (1-D) nanostructures are favorable for the hybrid polymer solar cells. In this dissertation, metal-organic chemical vapor deposition (MOCVD) is used to grow both of MgxZn1-xO polycrystalline 2-D films and single crystalline 1-D nanostructures for solar cells. A low-temperature (~250oC) ZnO buffer layer, followed by the high-temperature (~500oC) growth of MgxZn1-xO, is found to be beneficial for the formation of a 2-D dense and smooth film. On the other hand, a high-temperature (~520oC) ZnO buffer layer followed by a high temperature (530oC-560oC) growth of MgxZn1-xO is needed to grow the 1-D MgxZn1-xO (0≤x≤0.15) nanostructures on Si. For the first time, 1-D MgxZn1-xO nanostructures (0≤x≤0.1) are sequentially grown on a Ga-doped ZnO (GZO) 2-D film to form the 3-D photoelectrode, which is used to fabricate the P3HT-MgxZn1-xO hybride solar cells. The preliminary testing results of solar cells show that MgxZn1-xO is promising to be used in hybrid polymer solar cells for the enhancement of open circuit voltage (VOC). MgxZn1-xO (0≤x≤0.1) polycrystalline films are used in Cu2O-MgxZn1-xO heterojunction solar cells. The current density-voltage (J-V) measurements of solar cells under illumination show that VOC, shunt resistance Rsh and the solar conversion efficiency η are improved with increasing of Mg% until 10%. A relatively high solar conversion efficiency, ηAM1.5 = 0.71 % with a short circuit current JSC = 3.0 mA/cm2 and VOC = 575 mV, is obtained on the Mg0.1Zn0.9O sample. The band alignment between Cu2O and MgxZn1-xO is analyzed by using X-ray photoelectron spectroscopy (XPS) measurements.