Determination Of Spectral Responsivity Research Articles

Multijunction solar cell spectral response determination at radiation damage study

This paper discusses multijunction solar cells with optically coupled p-n junctions under radiation exposure photosensitivity spectral response study. It is shown that if the measurement technique does not consider the luminescent coupling and does not track the optical coupling degradation, then instead of a decrease (which is a natural response of a photoconverter to radiation damage), an abnormal increase in the narrow-bandgap photoresponse (receiving luminescent radiation) subcell due to radiation damage can be observed. Accordingly, with an increase in the irradiation dose, an increase in the subcell photocurrent forming a “negative” degradation dependence of MJ SC being used in space applications is recorded.

Calibration of photovoltaic reference cells by the global sunlight method

The global sunlight method for the calibration of reference photovoltaic cells is described and illustrated with results from recent measurements. In this method, the short circuit current of the solar cell is recorded as it tracks the sun's position. This current, corrected for temperature and total irradiance deviation, is then plotted against pressure-corrected geometric air mass (AM). The calibration value (CV) at standard test conditions (25 °C, 1000 W m−2 total irradiance with AM 1.5 spectral distribution) is extracted by a straight line fit to the data. The global sunlight method is less complex than other methods as it avoids (in particular conditions) the need for spectral irradiance measurements and corresponding relative spectral response determination. It has an estimated expanded uncertainty of 1% and agrees to better than 0.5% with the CVs of the World Photovoltaic Scale.

Comparison of ultraviolet data from colocated instruments from the U.S. EPA Brewer Spectrophotometer Network and the U.S. Department of Agriculture UV-B Monitoring and Research Program

Several ground-based ultraviolet (UV) monitoring networks exist in the United States, each of which is unique in the instrumentation employed for measurements. Two of these UV networks are the U.S. Environmental Protection Agency's (EPA's) Brewer Spectrophotometer Network and the U.S. Department of Agriculture's (USDA's) UV-B monitoring network, with a combined instrument total of 52 sites, with 32 sites located in the mainland United States. The Brewer records full sky spectra from 287 to 363 nm with 0.55-nm resolution, whereas the USDA instrument is a broadband device that measures broadband erythemally weighted UV data. To date, limited comparisons of data collected from these networks have been analyzed for comparative and quality assurance (QA) purposes. The data we use is taken from sites where instruments from each program are colocated, namely, Big Bend National Park, Texas, and Everglades National Park, Florida. To reduce the contribution of errors in the Brewer-based instruments, the raw data is corrected for stray light rejection, the angular response of the full sky diffuser, the temperature dependence of the instruments, and the temporal variation. This reduces the estimated errors of the absolute irradiance values of each Brewer spectral measurement to approximately ±5%. The estimated uncertainty of the USDA instruments is approximately ±6% with a systematic bias of (–13 to 5% depending on the total ozone) and is comprised of (1) standard lamp measurement errors, (2) spectral response determination, and (3) the angular response of the diffuser. We perform comparisons between the Brewer spectrally integrated and erythemally weighted UV irradiance measurements and the data collected by the broadband erythemal UV meters at colocated sites between 1997 through to 2002.

Spectral Response Based Calibration Method of Tristimulus Colorimeters.

A new method is described to calibrate tristimulus colorimeters for high accuracy color measurements. Instead of traditional lamp standards, modern, high accuracy detector standards are suggested for calibration. After high accuracy absolute spectral response determination of the tristimulus receivers, color (spectral) correction and peak (amplitude) normalization can minimize uncertainties caused by imperfect realizations of the Commission Internationale de l’Eclairage (CIE) color matching functions. As a result of the corrections, stable light sources of different spectral power distributions can be measured with an accuracy dominated by the sub tenths of a percent uncertainty of novel spectral response determinations.

The photoelectrochemical studies on CdS: Cu: Cl electrodes: Importance of photoconductivity effects

The photoelectrochemical characterisation of highly photosensitive and semi-insulating sintered pellets of CdS doped with Cu and Cl has been carried out. In the course of this work, we have observed a complete suppressin of the dark current but a pronounced photocurrent under cathodic polarisation. Both these observations indicate an unusual cathodic (i.e. forward bias) behaviour. It has been shown that due to a decrease in series resistance under illumination by an extrinsic photoconductivity effect, the “ideal” cathodic behaviour, i.e. normally found in dark for an n-CdS electrode with low resistivity, can get restored. We have also observed a red shift in the anodic photoelectrochemical spectral response of these samples. It is in agreement with our previous photoelectrochemical studies on CdS: Cu: Cl electrodes and can be explained by considering a Cu impurity excitation process. Additionally, we have observed that the background illuminations as such (employed in the “double-beam” technique of spectral response determination) do not alter the overall nature of the spectral response but result in an interesting photocurrent enhancement phenomenon. These photocurrent enhancement observations have been explained by taking into account the photoeffects at Cl-compensated Cu acceptor centers possessing a high capture cross section preferably for photoexcited holes.