A novel buffering technique for aqueous processing of zinc oxide nanostructures and interfaces, and corresponding improvement of electrodeposited ZnO-Cu2O photovoltaics
2011, Musselmann, Kevin, Marin, Andrew, Wisnet, Andreas, Scheu, Christina, MacManus-Driscoll, Judith, Schmidt-Mende, Lukas
A novel buffering method is presented to improve the stability of zinc oxide processed in aqueous solutions. By buffering the aqueous solution with a suitable quantity of sacrifi cial zinc species, the dissolution of functional zinc oxide structures and the formation of unwanted impurities can be prevented. The method is demonstrated for ZnO fi lms and nanowires processed in aqueous solutions used for the selective etching of mesoporous anodic alumina templates and the electrochemical deposition of Cu 2 O. In both cases, improved ZnO stability is observed with the buffering method. ZnO-Cu 2 O heterojunction solar cells (bilayer and nanowire cells) synthesized using both traditional and buffered deposition methods are characterized by impedance spectroscopy and solar simulation measurements. Buffering the Cu 2 O deposition solution is found to reduce unwanted recombination at the heterojunction and improve the photovoltaic performance.
Macroscopically uniform electrodeposited ZnO films on conducting glass by surface tension modification and consequent demonstration of significantly improved p–n heterojunctions
2011, Musselman, Kevin P., Gershon, Talia, Schmidt-Mende, Lukas, MacManus-Driscoll, Judith L.
An alternative water–ethanol zinc nitrate solution is demonstrated to completely eliminate macroscopic defects that are normally prevalent in ZnO films electrochemically deposited from aqueous zinc nitrate solutions. The inclusion of 25% ethanol (by volume) reduces the surface tension of the mixture and eliminates bubble formation on the conducting glass surface during deposition. To demonstrate the importance of film uniformity, the ZnO films are employed in ZnO–Cu2O n–p heterojunctions and an order of magnitude improvement in diode behaviour is observed.