Elucidation of optoelectronic properties of the sol-gel-grown Al-doped ZnO nanostructures

An optimized (1.0 wt%) sol-gel-grown Al-doped ZnO nanostructures by a controlled addition of suitable capping agents such as Squalane, Diethylenetriamine, Triethylene glycol dimethyl ether, Diethylamine and Diethylene glycol at the sol-gel synthesis stages in the sol mixtures, resulting the morphologies of nanosheets, sphere, aggregated disk and thin and thick plates. The as-grown sol was then used for the spin casting at 7000 rpm/30 s on a patterned ITO glass and analyzed in the inverted bulk-heterojunction solar cells. By employing such a nanostructured Al-doped ZnO layer, an improved efficiency of 3.2 % (130 % increase) was achieved in the spherical nanostructure (~40 nm) with a high fill factor (56.0) and a J _SC of 13.8 mA/cm² from the normal inverted solar cell (η = 1.34 % with J _SC = 5.8 mA/cm²). However, other nanostructured morphologies show varying efficiencies in the range of 1.12 and 2.41 %. The increase in short-circuit current density employing by spherical morphology can be attributed to the efficient interface energy step, increase in carrier concentration and smoother and uniform film that might influence a better percolation pathway and efficient charge collections.