Research Terms
Although there have been several proposed alternative materials for organic photovoltaic cells, they are comparatively inefficient to silicon-based photovoltaic cells. UCF researchers have developed a new, more effective and efficient way of utilizing organic materials within the organic photovoltaic cell.
Specifically, this invention involves an organic photovoltaic material comprised of a bulk heterojunction (BHJ) composition of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM), often referred to as P3HT:PCBM BHJ, providing improved performance in charge carrier extraction efficiency, especially from the anode side. This organic photovoltaic cell structure provides a work function in the nickel and indium doped tin oxide (Ni-ITO) material anode, in the range of -5.0 to -5.4 eV, thereby providing enhanced hole extraction.
Technical Details
This invention uses a Ni-ITO material layer as an anode to increase the work function of the anode for P3HT:PCBM BHJ organic photovoltaic cells. This invention's chemical composition provides enhanced hole charge carrier extraction, transport, and collection within an organic photovoltaic cell device that derives from the organic photovoltaic cell structure. The P3HT:PCBM BHJ composition can be used in multiple applications within non-limiting organic photovoltaic cell structures.
University of Central Florida researchers have created ZnO thin films with high crystalline quality, low defect, low dislocation densities, and sub-nanometer surface roughness by depositing on a low-temperature ZnO nucleation layer. By including a low-temperature ZnO nucleation layer on the substrate, the properties of the top wurtzite ZnO layer are enhanced improving the responsivity of the photodetector. While cubic MgZnO thin films with an Mg composition higher than 62 percent exist, they are low quality, and the photodetectors with these films only show low responsivity.
Most of the UV light from the sun is absorbed by the atmospheric ozone layer. In the solar-blind region, the ozone layer in our atmosphere absorbs nearly 100% of solar radiation for wavelengths shorter than 290 nanometers. UV detectors that have high sensitivity to UV-C and far UV radiation compared to radiation with wavelengths longer than 280 nm can be called "solar-blind." Conventional hexagonal lattice structures in semiconductors have suffered from various problems including cracking due to strain and reduced internal quantum efficiency. In addition, difficulties often arise from the lack of a suitable lattice-matched substrate, leading to higher dislocation densities. UV photodetectors and light emitters have drawn extensive attention, because of their wide field of use.
In aerospace and defense applications, UV photodetectors sense heat sources such as flames, jet engines, or missile plumes that emit light throughout the UV portion of the spectrum. By using these new semiconductor alloys in optoelectronic and microelectronic devices, the UV photodetectors can operate in the solar-blind region allowing for faster, more reliable detection of threats or consistent communications in space than compared to previous materials.
Technical Details
UCF researchers have overcome the difficulty of growing single wurtzite phase MgZnO with a high Mg concentration by adding a low-temperature ZnO nucleation layer on the substrate, such as that grown at 300-400°C. By changing the MgO concentration, gxZn1-xO has a tunable 25°C bandgap from 3.3eV for wurtzite ZnO to 7.8 eV for rock salt MgO. By tuning the Mg concentration and by controlling the Mg/Zn flux ratio during deposition, the process achieves a steep optical absorption edge of the wurtzite MgxZn1-xO with a spectral cutoff wavelength ranging from 278 nm to 377 nm. High crystal quality and optical quality single crystal MgxZn1-xO layers were grown epitaxially on c-plane sapphire substrates by plasma-assisted Molecular Beam Epitaxy (MBE). The photoconductors constructed with these films have demonstrated responsivity as high as ~102 A/W with a rejection ratio of two orders of magnitude in the solar-blind spectral range with a spectral cutoff of 278 nm.
Researchers at the University of Central Florida have developed new cubic semiconductor alloys for UV photodetectors and light emitters for applications in covert space-to-space communications, missile threat detection, and chemical and biological threat detection.
In aerospace and defense applications, UV photodectors sense heat sources such as flames, jet engines, or missile plumes that emit light throughout the UV portion of the spectrum. By using the UCF semiconductor alloys in optoelectronic and microelectronic devices, the UV photodectors can now operate in the solar blind region allowing for faster, more reliable detection of threats or consistent communications in space.
The upper ozone layer in our atmosphere absorbs nearly 100 percent of solar radiation for wavelengths shorter than 290 nanometers, creating the spectral region termed the solar-blind region. UV detectors that operate within this solar-blind region are optimized to have sensitivity to UV-C and far UV radiation but little to no response to ground level solar spectrum providing the application-specific spectral detection. These detectors use conventional hexagonal lattice structures in semiconductor photodetectors but suffer from various problems including cracking due to strain and reduced internal quantum efficiency. In addition, difficulties often arise from the lack of a suitable lattice matched substrate, leading to higher dislocation densities. UV photodetectors and light emitters have drawn extensive attention, because of their unique capabilities of detection and ability to withstand harsh environments.
Technical Details
The UCF semiconductor material comprises a single crystal cubic oxide substrate and an epitaxial cubic oxide alloy layer consisting of a transition metal or group IIA metal on the top surface of the substrate. The material has a sodium chloride structure, in which each of the two atom types form a separate face-centered cubic lattice, with the two lattices interpenetrating to form a 3D checkerboard pattern. Since there needs to be a matching of lattice structures between two different semiconductor materials to allow a region of band gap change without introducing a change in the crystal structure, the cubic epitaxial material is lattice matched within 5 percent to the lattice of the substrate and as low as 1.5 percent.
