Fabrication of InAs Submonolayer Quantum Dot Solar Cells Within InGaAs/GaAsSb Double-Well Structure

• Main Authors: Ting-Kai Yang, 楊庭愷
• Other Authors: Wei-Sheng Liu
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/c5m9r7

碩士 === 元智大學 === 電機工程學系丙組 === 107 === In this study, multistacked InAs submonolayer (SML) quantum dots (QDs) were sandwiched in an InGaAs/GaAsSb dot-in-a-double-well (DDwell) structure to enhance the crystal quality and optical properties of QDs. And improve the deivce performance of QD solar cell (QDSC) on the other hand. The photoluminescence (PL) intensity of the InAs SML QDs with the DDwell structure was 5.5 times higher than that of conventional InAs/GaAs SML QDs because of the reduced In-Ga intermixing and preserved QD dot size. Besides, the DDwell structure exhibited two peaks in reason of carrier overflowing from InAs SML QD to InGaAs quatntum well. The QDs with the DDwell structure enhanced the activation energy from 41.7 to 101.8 meV among the compared samples since the carrier thermal escape was suppressed in the InAs SML QDs. These improved optical properties of the InAs SML QDs with the DDwell structure can be attributed to the improved crystalline quality because of the use of Sb surfactants and additional volume for radiative recombination provided by the InGaAs quantum well. In high-resolution transmission electron microscopy, the microstructures of the InAs SML QDs showed larger dots for the DDwell structure, thus verifying the elongated emission wavelength in PL measurement. The external quantum efficiency revealed that SML QD with DDwell structure solar cell extended the absorbing limit from 910 nm to 960 nm; this structure also enhanced the open circuit voltage to 0.73V and short current density to 17.97 mA/cm2.