Atomic Layer Deposition of PbS-ZnS quantum wells for high-efficiency solar cells

Quantum confinements such as quantum wells, wires, and dots posses several advantages for next-generation solar cells. In this study, we present results on quantum confinement in PbS-ZnS quantum wells deposited by Atomic Layer Deposition (ALD). Materials selection criteria are presented with a focus on the properties of the well and barrier material. PbS quantum wells embedded in thin ZnS barrier layers are shown to demonstrate quantum confinement effects through scanning tunneling microscopy (STM). The band gap of the PbS films has been varied from 0.4-1.0 eV by varying the number of ALD cycles. The bandgap variation with film thickness is well matched to results predicted by effective-mass theory.