Abstract
For examining the carrier movements through tunnel junction, electrically and optically-biased photoreflectance spectroscopy (EBPR and OBPR) were used to investigate the internal electric field in the InGaP/GaAs dual junction solar cell at room temperature. At InGaP and GaAs, the strength of p-n junction electric fields (Fpn) was perturbed by the external DC bias voltage and CW light intensity for EBPR and OBPR experiments, respectively. Moreover, the Fpn was evaluated using the Fast Fourier Transform (FFT) of the Franz—Keldysh oscillation from PR spectra. In the EBPR, the electric field decreased by increasing the DC bias voltage, which also decreased the potential barrier. In OBPR, when incident CW light is absorbed by the top cell, the decrement of the Fpn in the GaAs cell indicates that the photogenerated carriers are accumulated near the p-n junction. Photogenerated carriers in InGaP can pass through the tunnel junction, and the PR results show the contribution of the modification of the electric field by the photogenerated carriers in each cell. We suggest that PR spectroscopy with optical-bias and electrical-bias could be analyzed using the information of the photogenerated carrier passed through the tunnel junction.
Highlights
Semiconductors play an important role in solar cell technology, where the solar cell’s main parameter is high efficiency
The Optically Biased Photoreflectance (OBPR) signals are related to the absorption of a CW light
The built-in electric field and its dependence on the external-bias voltage and external CW light were evaluated by the Fast Fourier Transform (FFT) analysis of the Franz—Keldysh oscillation (FKO) in the PR spectrum
Summary
Semiconductors play an important role in solar cell technology, where the solar cell’s main parameter is high efficiency. One method to analyze the current matching of multijunction SC is studying the internal electric field in each cell’s p-n junctions It can provide information about the carriers’ movement generated by the illuminated light through the tunnel junction to improve the current matching. The photovoltaic effect on the internal electric field is an important parameter in investigating the current matching in multi-junction solar cells [5]. The electrical and optical biased photoreflectance (EBPR and OBPR) is used to examine the tunneling effect on the carrier density movement in this study’s dual junction solar cells. The DC bias voltage and CW light’s internal electric field variation are measured to investigate the tunnel junction effect on the carrier density
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