Researchers Deposit Nanoparticles on Large Area
Researchers at the NSF-funded Engineering Research Center (ERC) for Quantum Energy and Sustainable Solar Technologies (QESST), which is headquartered at Arizona State University, have demonstrated a method to deposit nanoparticles as a coating on substrates up to five inches on a side. The coating process accelerates aerosolized silicon nanoparticles by passing them through a slit-shaped nozzle, across which there is a large pressure drop, and the resulting spray of high-velocity particles impinges on a substrate under the nozzle, thereby depositing a coating of controllable thickness and porosity.
Evidence of successful implementation of nanomaterials into a suitable photovoltaic (PV) form would dramatically change the PV landscape and accelerate a path to a terawatt-PV future; but there are very significant challenges. This work demonstrates a step toward implementation by arranging nanomaterials, silicon in particular, into a PV-friendly form—a coating.
Efficiency is presently the largest driver in the silicon PV market, and, with recent commercial cell efficiencies over 25%, it is becoming clear that silicon will plateau in coming years as it approaches the single-junction Shockley-Queisser limit (a bit over 30%). Nanomaterials have the potential (in principle) to approach and exceed this limit—for example, via multi-junction designs that employ tunable absorption, complete absorption with very thin layers, and generation of more than one electron-hole pair per absorbed photon.
Nanomaterials are most commonly cast from solution onto substrates to form films, but a drawback of this approach is that the coating morphology depends on the solvent-particle and solvent-substrate interactions—change any of the three and the resulting film changes too. The spray process, however, is free of this limitation; because of its physical nature, the technique can deposit nanoparticles of any material onto a substrate of any material and with nearly any surface morphology (see figure).