No abstract

No abstract

Hole transitions from the heavy-hole ͑hh͒ to the light-hole ͑lh͒ band contributing to the 4-10 m response range are reported on p-GaAs/ AlGaAs detectors. The detectors show a spectral response up to 16.5 m, operating up to a temperature of 330 K where the lh-hh response is superimposed on the free-carrier response. Two characteristic peaks observed between 5-7 m are in good agreement with corresponding energy separations of the lh and hh bands and thus originated from lh-hh transitions. Results will be useful for designing multi-spectral detection which could be realized on a single p-GaAs structure.

No abstract

The efficiency of dye-sensitized solar cells may be further improved if ways are found to broaden the spectral response resolving the fundamental issues involved. Here we report construction of dye-sensitized solid-state photovoltaic cells with heterostructure configurations:  [1] n-TiO2/D1/p-CuSCN, [2] n-TiO2/p-CuSCN/D2/ p-CuSCN and [3] n-TiO2/D1/p-CuSCN/D2/p-CuSCN, where n-TiO2 is a ∼10 μm thick nanocrystalline film of titanium dioxide, p-CuSCN and p-CuSCN are thin (∼ 2 nm) and thick (∼ 10 μm) films of copper(I) thiocyanate. Monolayers of the dyes D1 (Fast Green) and D2 (Acridine Yellow) are coated on TiO2 and p-CuSCN, respectively. The cell of configuration [3] delivered the highest efficiency, open-circuit voltage, and short-circuit photocurrent as it effectively utilizes the light adsorbed by D1 and D2. The mechanism of operation involves tunneling of energetic electrons and holes liberated in photoexcitations of dyes through a thin barrier of p-CuSCN. The strategy adopted indicates the possibility of designing more efficient dye-sensitized solar cells, widening the spectral response.