Ultra-thin and light weight cadmium telluride (CdTe) solar cells were fabricated on 20-micron thick yttria-stabilized zirconia (3YSZ) substrate in superstrate configuration. Optimization of CdCl2 treatment and copper diffusion were done to enhance the preformation of the device. Due to high reflectance off the substrate surface, anti -reflecting layer was deposited on the front of the device to reduce the reflectance which increase current density. Here, we present ultra-thin and light weight CdS/CdTe solar cells with conversion efficiency of 11.2 % and specific power> 6 kW/kg. This could make CdTe based solar cells applicable for space applications.

We report an innovative, low-cost, solid-state neutron detector based on the technology of thin-film CdTe solar cells activated with layers of isotopically enriched metallic Li-6. The technology leverages recent advances in thin-film solar-module manufacturing and lithium sources for electrochromic window fabrication. Our detector inherently has very high rejection of gamma events and strong directional sensitivity; it is readily scalable in size from personal radiation monitors to radiation portal monitors. The thermal neutron response of a double detector stack is competitive with and/or exceeds responses reported for other portable detectors such as a small He-3 tube, a CLYC-based scintillator, or a microstructured semiconductor detector.

Copper diffusion from the back contact degrades the performance of CdTe solar cells over time and increases the levelized cost of electricity production from CdTe photovoltaics. Recently, carbon single-wall nanotubes (SWNTs) were shown to be a Cu-free, stable alternative that preserves the device efficiency (Phillips et al., Nano Letter, 2013). Large diameter tube samples containing a mixture of semiconducting (s-SWNT) and metallic (m-SWNT) species were used in the previous work, and the mechanisms leading to a low back barrier for majority carrier flow were not clear. The good performance of the back contact was ascribed to the interaction between the s-SWNTs in the film and the polycrystalline facets of the CdTe surfaces. In that case, the s-SWNT species had small bandgaps (~0.6-0.8 eV). Here, in an attempt to develop a more detailed understanding of the SWNT/CdTe back contact, we employed SWNT samples that are predominantly semiconducting (95%) and of larger bandgap (~1.1-1.3 eV). The power conversion efficiency of these unoptimized devices was 11.5 % with a s-SWNT back contact, as compared to 11.2% with a standard Cu/Au back contact.

The optical and electrical properties of the glass superstrate and window layer materials play critical roles in the performance of CdTe photovoltaic devices. The compositional modifications made to tailor the transmission spectra in these materials so as to maximize the Jsc of the device will be reviewed. Progress towards improving the electrical characteristics (e.g., carrier mobility) of the transparent conductive oxides as well as materials design to improve the interface behavior at the window layer will be presented. Recent results showing the impact of these changes on achieving thinner CdS window layers and improved device performance in devices made by both thermal and energetic deposition methods will be discussed.

We have discovered that films of carbon single wall nanotubes (SWNTs) make excellent back contacts to CdTe devices without any modification to the CdTe surface. Efficiencies of SWNT-contacted devices are slightly higher than otherwise identical devices formed with standard Au/Cu back contacts. The SWNT layer is thermally stable and easily applied with a spray process, and SWNT-contacted devices show no signs of degradation during accelerated life testing.

L'invention concerne une structure de cellule photovoltaique comprenant une couche tampon/de passivation au niveau de l'interface tellure de cadmium (CdTe)/contact arriere. La couche tampon/de passivation est constituee du meme materiau que la couche active a semi-conducteur de type n. Dans une certaine forme de realisation, la couche tampon et la couche active a semi-conducteur de type n sont constituees de sulfure de cadmium (CdS). Un procede de realisation de cellule photovoltaique comprend l'etape consistant a former les couches actives a semi-conducteur et la couche tampon/de passivation dans la meme chambre de depot et en utilisant la meme source de materiau.