Pulsed Potential based E-ALD of PV Materials

Tuesday, 7 October 2014: 10:40
Expo Center, 1st Floor, Universal 12 (Moon Palace Resort)
J. L. Stickney, J. Czerniawski, and B. Perdue (The University of Georgia)
A family of absorber materials of interest for high volume production of photovoltaics is referred to as CZTS, or Cu2ZnSn(S,Se)4.  The primary advantages of these materials are that they are made from nontoxic earth abundant elements.   This group has been working on E-ALD as a method for the formation of materials an atomic layer at a time for many years.  E-ALD provides atomic level control during the growth process and has been shown to form high quality deposits.  E-ALD is based on alternating precursor solutions of the desired elements and the use of UPD to limit growth to an atomic layer at a time.   The E-ALD method has important advantages for the formation of nanofilms of materials.   There are a broad range of new PV designs involving nanostructured electrodes and plasmonic layers where the thickness of an absorber layer can be much thinner than the µm needed for a typical thin film PV.   On such substrates, E-ALD should show important advantages for the formation of conformal nanofilms without annealing.  The main disadvantage to the use of E-ALD for the growth of PV, is the time it takes to grow a µm thick absorber layer.  The rate of growth is presently limited by the time it takes to change solutions.    Efforts by this group are being directed to the development of a variant of E-ALD based on potential changes, pulses, rather than solution exchanges.   This greatly increases the rate of deposition.   Presently, the Authors referred to it as potential pulse ALD (PP-ALD).   Preliminary results on the formation of Cu2Se and other components of a CZTS buffer layer will be discussed.