Effect of temperature on the intensity and carrier lifetime of an AlGaAs based red light emitting diode

The influence of temperature on the intensity of light emitted by as well as the carrier life time r of a standard A1GaAs based light emitting diode has been investigated in the temperature range from 345 to 136 K. The open-circuit voltage decay （OCVD） technique has been used for measured the carrier lifetime. Our experimental results reveal a 16% average increase in intensity and a 163.482-19.765 ns variation in carrier lifetime in the above temperature range. Further, theoretical and experimental analysis show that for negligible carrier density the intensity is inversely proportional to carrier lifetime for this sample.

Influence of temperature on tunneling-enhanced recombination in Si based p–i–n photodiodes

We investigate the dominant dark current transport mechanism in Si based p-i-n photodiodes, namely, BPW 21R, SFH 205FA and BPX 61 photodiodes in the temperature range of 350 to 139 K. The forward current- voltage characteristics of these photodiodes are explained via the tunneling enhanced recombination model, which gives a quantitative description of the electronic mechanism in the p-i-n junction photodiodes. The observed tem- perature dependence of the saturation current and the diode ideality factor of these devices agree well with theo- retical predictions; the analysis also indicates the importance of doping for enhancement of tunneling. The present study will be helpful in applying the devices at low temperature ambience.

Effect of single walled carbon nanotubes on series resistance of Rose Bengal and Methyl Red dye-based organic photovoltaic device

The influence of single walled carbon nanotube（SWCNT）on the series resistanceof Rose Bengal（RB）and Methyl Red（MR）dye-based organic diodes has been studied.It has been revealed from experimental results that SWCNT has a significant effect on Rs.The values of Rs are measured from current–voltage（I–V）characteristics and also by utilizing the Cheung method.Obtained values from the Cheung method have been verified using H（I）–I plots for all dye-based devices.The extracted values using these two processes show a good consistency with each other.It is observed that Rs is reduced significantly by incorporating SWCNT for both dyes.The estimated amounts of reduction of Rs using SWCNT are 76.08%and 64.23%obtained from the I–V relationship whereas the value of Rs shows a reduction of 83.5%and 67.1%when measured by using the Cheung method for RB and MR dyes respectively.The ideality factor and barrier height of the diodes have also been extracted.The ideality factor has decreased with incorporation of SWCNT.A reduction in barrier height for the devices has also been observed in the presence of SWCNT.

Effect of COOH-functionalized SWCNT addition on the electrical and photovoltaic characteristics of Malachite Green dye based photovoltaic cells

We report the effect of COOH-functionalized single walled carbon nanotubes（COOH-SWCNT） on the electrical and photovoltaic characteristics of Malachite Green（MG） dye based photovoltaic cells. Two different types of photovoltaic cells were prepared, one with MG dye and another by incorporating COOH-SWCNT with this dye. Cells were characterized through different electrical and photovoltaic measurements including photocurrent measurements with pulsed radiation. From the dark current–voltage（I–V） characteristic results, we observed a certain transition voltage（Vth/ for both the cells beyond which the conduction mechanism of the cells change sharply. For the MG dye, Vthis 3.9 V whereas for COOH-SWCNT mixed with this dye, Vthdrops to 2.7 V. The device performance improves due to the incorporation of COOH-SWCNT. The open circuit voltage and short circuit current density change from 4.2 to 97 m V and from 108 to 965 A/cm2 respectively. Observations from photocurrent measurements show that the rate of growth and decay of the photocurrent are quite faster in the presence of COOH-SWCNT. This observation indicates a faster charge separation processes due to the incorporation of COOHSWCNT in the MG dye cells. The high aspect ratio of COOH-SWCNT allows efficient conduction pathways for the generated charge carriers.