Climate change is a reality and a move away from fossil fuels to renewable energy technologies is an essential part of mitigation efforts. Photovoltaics (PV) provide a way to generate clean and renewable energy from a ubiquitous source. Despite this,fossil fuels are still deeply entrenched in the global energy system, in part due to their low cost. Silicon solar cells currently dominate the PV market,however, their levelised cost is relatively high compared to other energy technologies. Therefore, if PV is to achieve its full potential, there is a need to develop low cost solar cells to enable global uptake of this promising technology.
The aim of this research was to demonstrate a nanocrystal (NC) activated Schottky barrier solar cell fabricated using relatively ambient processes. Ti film was anodised or thermally oxidised and the Schottky barrier was subsequently formed at the interface between TiO2 and the noble metal, Au, Ag, or Pt, which were sputtered, evaporated or dropcast in nanowire (NW) form. In the absence of activating nanocrystals, the Schottky barrier functions as an efficient cell but only for UV light due to the wide band gap of TiO2. Nanocrystals with a narrower band gap were deposited on the Schottky barrier to extend the response into the visible region.
The cells fabricated with Ag NWs and Pt provided the largest Schottky barrier heights of 1.02 eV and 1 eV respectively. The Pt device obtained the largest UV photoresponse of 390 μAcm-2 and 721 mV at 330 nm, and external quantum efficiency (EQE) of 18% at 330 nm. The Pt and AgNW cells were subsequently activated with CdS, CdSe, CuO, CuInS2 and CdTe NCs. The CdS-NC/Pt, CdS-NC/Ag-NW, and CuInS2-NC/Ag-NW devices, in particular, provided proof-of-concept, generating a UV photoresponse from the TiO2 and a visible photoresponse from the NCs consistent with the respective band gaps. The optimum EQE measured for the CdS-NC/Pt device was 0.04% at 470 nm. Hence, this work demonstrates the NC activated Schottky barrier solar cell and provides a possible low cost fabrication route for future development.
