Project objectives
The issues that this project attempts to address are long-range fundamental research issues that, if solved, will make it possible to leap-frog solar cells efficiencies from current peak values of 44.4 % to values above 50 %.
The project has several clearly defined but interconnected objectives.
Objective 1. The growth, treatment, and characterization of lattice-matched bandgap-engineered (x»3y) dilute-nitride (x≤1%) Ga1-xInxNyAs1-y/GaAs alloys with significantly improved electrical and optical properties suitable for achieving high conversion efficiencies (ideally close to the theoretical values) when integrating in an intermediate band solar cell.
- This objective specifically addresses the current unavalability materials systems capable of successfully working as intermediate band photovoltaics, via technologies based on GaAs substrates. It also addresses the rapid degradation of dilute nitride alloys with nitrogen content.
Objective 2. The design, growth, processing and characterization of IBSCs containing engineered GaInNAs/GaAs alloys showing significantly improved photocurrents with minimal drop in photovoltage.
- This objective addresses the current large photovoltage drop in IBSCs containing dilute nitride GaNAs(P)(Sb) materials capable of demonstrating significant enhancement in generated photocurrent.
Objective 3. The growth and characterization of device-quality BzInxGa1-x-zN/GaN alloys with dilute boron and low indium contents (z≤5%,x<20%) and strained engineered In(Ga)N/BInGaN/InGaN QDs array for IBSCs applications.
- This objective addresses the possible strain-related deterioration of a highly strained In(Ga)N/InGaN QDs array when an increased number of layers are added to the array for photocurrent enhancement when integrated in a IBSCs. Also it addresses the problems occurred with incorporation of a large amount of In into GaN needed for optimization of IB levels in multiple IBSCs based on In(Ga)N/InGaN/GaN QDs material.
Objective 4. The design, growth, fabrication and characterization of intermediate band solar cells on GaN substrates containing bandgap and strained-engineered multiple-layers In(Ga)N/BInGaN/InGaN QDs with enhanced photocurrents and minimal photovoltage drop.
- This objective addresses the current bottleneck of a significant photovoltage drop in In(Ga)N/GaN QDs IBSCs capable of generating remarkable photocurrents and hence high conversion efficiencies.
The project Outcomes:
- Innovative technology for improving the transport and optical properties of lattice-matched dilute nitride quaternary GaInNAs/GaAs alloys (N≤1%) by electron irradiation and subsequent thermal annealing.
- Innovative technology for growth by MBE of high quality BInGaN/GaN epitaxial layers with dilute boron content up to 5% and indium content < 20%.
- Experimental and functional models of GaInNAs-based IBSCs with improved conversion efficiencies.
- Experimental and functional models of strain engineered In(Ga)N/BInGaN/GaN QDs intermediate band solar cells with improved conversion efficiencies.
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