Papers by Keyword: Bragg Reflector

Abstract: Feasibility to increase the radiation resistance of multijunction solar cells in using Bragg reflectors has been shown. Two designs of Bragg reflectors for multijunction solar cells, which allow ensuring in the Ga(In)As subcell base an effective collection of minority charge carriers at the decrease of their diffusion length caused by radiation treatment, have been investigated. Influence of subcells’ thicknesses of n-p GaInP/Ga(In)As/Ge solar cell under 1 MeV electron irradiation with fluences up to 3•1015 cm–2 on short circuit current was considered. Optimal thicknesses of GaInP and GaInAs subcells with Bragg reflectors, depending on the rated operation period on the geostationary orbit, were estimated. It has been shown that such an optimization allows to achieve efficiency at long operation of solar cells on the orbit noticeably higher than that of non-optimized cells.

Abstract: We studied the different carrier kinetic mechanisms involved into the interband absorption of quantum dots (QDs) by photocurrent spectroscopy. It was shown that in vertically coupled InGaAs QDs an effective carrier emission, collection and separation take place due to minizone formation. The possibility for the incorporation of vertically-coupled QDs into solar cells (SC) without any deterioration of structural quality of the p-i-n-junction has been shown. Due to the additional absorption of solar spectrum in QD media and the subsequent effective separation of photogenerated carriers, an increase (~1%) in short-circuit current density (Jsc) for the QD SC-devices has been demonstrated. However the insertion of QDs into intrinsic region reduced the open circuit voltage (Voc) of such devices. Moving the QD array in the base layer as well as including the Bragg reflector (BR) centered on 920 nm resulted in increase of the Voc. Moreover an improved absorption in the QD media for SC with BR led to further increase of Jsc (~1%). The efficiency for QD SCs at the level of 25% (30 suns AM1.5D) has been demonstrated.

Abstract: In this paper we discussed the relation between depth errors that happened in films growth and incidence angle variation on DBR reflectivity. We assume that there is 10% depth error in high and low index materials, and there are four plus one situations to be considered. Four are combinations of Hi +/- 10% error and Lo +/- 10% error, and no error. Our simulation results show that the depth error makes the reflective band shift and it almost doesn’t reduce reflectivity. The thickness error of +/- 10% in (Al0.4Ga0.6N/GaN) DBR structure (15 pairs) at 420nm was 42nm. A theoretical analysis using Transfer Matrix Mode with MATLAB software on the influence of layer thickness and incidence angle variation in vertical-cavity surface-emitting lasers with distributed Bragg reflectors (DBRs) on lasing wavelength is presented. It is shown that changing the thickness of the layers in the DBR mirror by only 10% is sufficient to produce shifts in the peak reflectance wavelength up to ± 20 nm (for a blue laser at 420nm). This could limit the precision of a desired wavelength, which is its reproducibility.