PbS Quantum-Dot Depleted Heterojunction Solar Cells Employing CdS Nanorod Arrays as the Electron Acceptor with Enhanced Efficiency

Depleted heterojunction (DH) solar cells have shown great potential in power conversion. A 3-D DH structure was first designed and fabricated through a layer-by-layer spin-coating technique to increase the interfacial contact of p-type PbS quantum dots (QDs) and n-type CdS nanorod arrays. As a result, a decent power conversion efficiency of 4.78% in this structure was achieved, which is five times the efficiency of a planar heterojunction structure of a similar thickness. In the 3-D DH structure, n-type CdS nanorod arrays (NRs) were grown vertically as electron acceptors, on which p-type PbS quantum dots were deposited as absorbing materials in a layer-by-layer spin-coating fashion. The results are discussed in view of effective transportation of electrons through CdS NRs than the hopping transportation in large nanoparticle-based CdS film, the enlarged interfacial area, and shortened carrier diffusion distance.