High Performance and Cost-Effective Nanopillar Photovoltaics

Solar energy represents one of the most abundant and yet least-harvested source of renewable energy. In recent years, tremendous progress has been made in developing photovoltaics (PVs) that can be potentially mass employed.

Of particular interest to cost-effective solar cells is to utilize novel device structures and materials processing for enabling acceptable efficiencies. In this regard, we have recently demonstrated the direct growth of highly regular, single crystalline nanopillar (NPL) arrays of optically active semiconductors on aluminum substrates which are then configured as solar cell modules.

As an example, we have demonstrated a PV structure that incorporates 3D, single crystalline n-CdS NPLs, embedded in poly-crystalline thin films of p-CdTe, to enable high absorption of light and efficient collection of the carriers. Through experiments and modeling, we have demonstrated the potency of this approach for enabling highly versatile solar modules on both rigid and flexible substrates with enhanced carrier collection efficiency arising from the geometric configuration of the NPLs. So far, materials conversion efficiency of ~12% with a device conversion efficiency of ~6% (50% optical transparency loss from the unoptimized top contact) are attained in our first generation solar modules.

This approach, which is compatible with a wide range of semiconductor materials, could potentially have a large impact in the realization of efficient and light weight solar panels. We are exploring various device architectures and material systems based on this process scheme to further enhance the efficiency of the enabled cells.