Energy Band Engineering for Low Cost Photovoltaics with Abundant Materials

Project: Research

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Description

Efficient utilization of the solar energy requires materials with electronic bandstructures that are tuned to absorb a large portion of the sun light and convert it intoelectrical power. Another important consideration is that these materials have to beearth abundant enough to produce photovoltaics for the global gigawatt scale demand.Moreover, it is highly desirable that these materials are also non-toxic so that theirimpact on the environment is minimal. Compound semiconductors composed ofabundant elements such as oxides and sulfides typically have energy gaps too large forefficient solar power conversion. We have discovered that alloying of distinctly differentmaterials leads to materials whose electronic band structure can differ drastically fromthe band structure of the component materials. These highly mismatched alloys (HMAs)offer an unprecedented flexibility in controlling not only the band gap but also thelocation of the conduction and the valence band edges. However, because of the highmismatch in electronegativity and size of the elements, synthesis of these alloys requirestechniques that are highly non-equilibrium in nature. In this proposal our goal is todevelop highly disruptive future-generation solar energy technologies based on ourrecently discovered highly mismatched semiconductor alloys. In simple terms we proposeto synthesize a semiconductor material with a small energy gap within the solarspectrum by alloying two judiciously selected semiconductors with the large energy gapsoutside the solar spectrum. We use the band anticrossing model to identify a class ofwide gap compounds of light, abundant elements, namely zinc oxide alloying with zincsulfide, selenide and telluride that exhibit extreme band gap bowings resulting in amuch lower band gaps, well within the range necessary for efficient solar powerconversion. Such ZnO-based HMAs are formed of abundant and non-toxic elementsand are expected to exhibit high chemical and thermal stabilities as well as a superiortunability in electronic properties. Moreover, we propose to exploit the electronic bandtuning capability of ZnO based HMA to fabricate a hybrid ZnO HMA-Si double junctiontandem solar cell that is expected to achieve efficiency over 30%. We plan to carry out a2 phase project—in phase I we focus on material synthesis and characterization of ZnObased HMAs; in phase 2 we will utilize the results obtained in phase 1 to design,fabricate and test prototype single and multijunction solar cells.

Detail(s)

Project number9042238
Grant typeGRF
StatusFinished
Effective start/end date1/01/162/06/20

    Research areas

  • Photovoltaics,electronic band structure,Highly mismatched alloys,band gap engineering,