Special Materials Research Seminar

Photovoltaic (PV) solar cells convert solar energy to electricity using combinations of semiconducting sunlight absorbers and metallic materials as electrical contacts. Novel nanoscale materials introduce new paradigms for ultrathin, lightweight, solution processable PV as an alternative to conventional Si technology. In addition, the optical absorption, band gap, and charge carrier mobility of nanoscale materials can be tuned by tailoring their chemistry or using quantum confinement effects, thus creating novel opportunities for efficient solar cells. From the viewpoint of the fundamental processes involved in PV operation, nanoscale PV poses additional challenges due to the formation of strongly bound electron-hole pairs (excitons) upon photoabsorption requiring the presence of so-called donor-acceptor (D-A) semiconductor heterointerfaces within the active layer to dissociate excitons and generate charge carriers.

My seminar will discuss the computational study of two novel classes of materials for nanoscale PV with a range of benefits including optical absorption, stability, tunability, and carrier mobility superior to materials employed so far in nanoscale PV. To this end, we employed computational methods such as density functional theory and the GW-Bethe-Salpeter approach, and further developed a framework to predict exciton dissociation at D-A interfaces and estimate efficiencies in nanoscale PV. Proof-of-concept PV devices were fabricated and tested in collaboration with experimental research groups.

The two material families discussed in this talk include carbon nanomaterials, for which we show the computational design and experimental realization of solar cells with an efficiency of 6.3% coupled to superior photostability, and two-dimensional monolayers including graphene, boron nitride, and transition metal dichalcogenides (TMD) such as MoS2 and WS2. We will focus on the extraordinary sunlight absorption of TMD monolayers and their unique potential to develop 1 nm thick solar cells with unprecedented power density.