Evaluation of radiation degradation of GaAs solar cells with InGaAs quantum dot layers using radiation induced current

照射誘起電流を用いたInGaAsドット層を含むGaAs太陽電池の放射線劣化評価

大島 武; 中村 徹哉*; 住田 泰史*; 今泉 充*; 佐藤 真一郎; 菅谷 武芳*; 松原 浩司*; 仁木 栄*; 望月 透*; 岡野 好伸*

Oshima, Takeshi; Nakamura, Tetsuya*; Sumita, Taishi*; Imaizumi, Mitsuru*; Sato, Shinichiro; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*; Mochizuki, Toru*; Okano, Yoshinobu*

Introduction of highly-stacked well-aligned Quantum Dots (QDs) layers into solar cells are expected to realize their extremely high conversion efficiency. In this study, the current induced in QD solar cells by 1 MeV electron irradiation was evaluated to investigate their degradation response. The samples used in this study were GaAs PiN solar cells with InGaAs QD layers by molecular beam epitaxy (MBE). For comparison, GaAs PiN solar cells with an i-layer were fabricated under the same process without the fabrication of the QD layers. The QD and non QD solar cells were irradiated with 1MeV electrons and their electron-induced currents were measured at applied bias between -300 and 200 mV. As a result, QD solar cells showed applied bias dependence of electron-induced current, and the value of electron-induced current increased with increasing reverse bias. Also, with increasing electron fluence, the electron-induced current decreased. This can be interpreted in terms of a decrease in carrier lifetime due to radiation induced defects. The applied bias dependence for QD solar cells became larger with increasing electron fluence. On the other hand, non QD solar cells did not show the applied bias dependence of electron-induced current before and after irradiation. These results suggest that carriers generated in QD solar cells by electrons recombine in QD layer when the electric field is not high enough.