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Top: Schematic of InAlAs/InP solar cell showing layer thickness and composition. Blue: window . Light gray: absorber . White: cap . Yellow: metallic contacts. Bottom: Photograph of fabricated InAlAs solar cells with each.
X-ray diffraction measurement and simulation of the cell structure showing a pseudomorphic window layer. Window broad peak and fringes correspond to a 20 nm unrelaxed layer. Measurement settings: , (0 0 4) reflection, receiving slit: 1/2°.
(a) Room temperature photoluminescence measurement of the 300 nm layer as a function of wavelength showing material bandgap and alloy/InP interface peak. (b) Time-resolved photoluminescence measurement on the same alloy showing a lifetime of 206 ps. The dashed line corresponds to the exponential decay behavior.
(a) Light I-V curve under AM 1.5 global illumination for the fabricated InAlAs solar cells using a 1.7 eV window layer (squares), a 2.0 eV window layer (diamonds), and a 2.0 eV window plus an InGaAs cap layer and antireflection (AR) coating (circles). Best cell characteristics are shown in Table I. (b) External quantum efficiency (EQE) of the InAlAs cell with cap layer and AR coating as a function of light wavelength.
InAlAs solar cell figures of merit obtained by one device modeling14 of the structure shown in Fig. 1 without and with a 20 nm thick InAlAs top window layer with different compositions and therefore band gap energies. The modeling takes multiple internal and external reflections into account and normal incidence of light. The last row shows the parameter measured for the InAlAs solar cell with windows, cap layer, and an antireflection coating. In all cases EQE refers to the maximum value of the external quantum efficiency achieved at 765 nm.
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