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Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sato, Shinichiro; Sugaya, Takeyoshi*; Mochizuki, Toru*; Okano, Yoshinobu*; Oshima, Takeshi
Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.73 - 76, 2015/11
The radiation effect on GaAs p-i-n solar cells with quantum dot (QD) in the i-layer was investigated. In a previous work, we particularly noted the degradation of fill-factor (FF) for the QD cells. In this work, to clarify the reason of the FF degradation in QD cells, generation current due to low-energy proton irradiation, which we call ion beam induced current (IBIC), was observed to characterize behavior of the generated minority carrier by the protons in the depletion region where QDs are located. The energy of protons was adjusted to damage the depletion region, and decrease of generation current was measured during the proton irradiation. The results suggest that the serious degradation of FF is caused by a decrease of the carrier collection efficiency in the depletion region due to proton damage.
Oshima, Takeshi; Sato, Shinichiro; Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*
Solar Energy Materials and Solar Cells, 108, p.263 - 268, 2013/01
Times Cited Count：13 Percentile：49.45(Energy & Fuels)GaAs solar cells which have a PiN structure with 50 self-organized In
Ga
As Quantum Dot (QD) layers were irradiated with 1 MeV electrons up to 1
10
/cm
. After irradiation at 110/cm, the remaining factor of I
, V
and P
for the InGaAs 50 QD solar cell becomes 80, 90 and 55% of the initial values, respectively. On the other hand, those values for non QD GaAs solar cells decrease to 95, 80 and 63% of the initial values, respectively. Since the i-layer for the 50 QD solar cells (1.1 
m) is thicker than the non QD solar cells (660 nm), the larger degradation of I for the 50 QD solar cells than the non QD ones can be interpreted in terms that the carrier recombination in the i-layer for the 50 QD solar cells is larger than that for the non QD solar cells. For V, the 50 QD solar cells showes better radiation resistance than the non QD solar cells. Furthermore, the annealing behavior of the electrical characteristics for the 50 QD and the non QD solar cells was investigated at RT under AM 0 immediately after the irradiation. As a result, the recovery of the electrical characteristics for both solar cells was observed, and the GaAs solar cells shows relatively larger recovery compared to the 50 QD solar cells. Although the mechanism of this recovery has not yet been clarified, the origin of this recovery is thought not to come from the existence of QDs because the GaAs solar cell without QD layers also shows the recovery.
Oshima, Takeshi; Sato, Shinichiro; Imaizumi, Mitsuru*; Sugaya, Takeyoshi*; Niki, Shigeru*
Proceedings of 37th IEEE Photovoltaic Specialists Conference (PVSC-37) (CD-ROM), p.1605 - 1609, 2011/06
Oshima, Takeshi; Sato, Shinichiro; Morioka, Chiharu*; Imaizumi, Mitsuru*; Sugaya, Takeyoshi*; Niki, Shigeru*
Proceedings of 35th IEEE Photovoltaic Specialists Conference (PVSC-35) (CD-ROM), p.002594 - 002598, 2010/06
Times Cited Count：3 Percentile：78.38(Energy & Fuels)Quantum Dot (QD) solar cells are regarded as promising candidate for solar cells with superior high efficiency. For space application, it is important to understand radiation effects in such QD solar cells. However, radiation response of QD solar cells has not yet been clarified. In this study, we irradiate QD solar cells with electrons, and investigate change in the electrical performance of the QD solar cells. PiN structure solar cells with self-organized InGaAs QD layers grown on GaAs (001) substrates by MBE were used in this study. The efficiency for the 30 QD layer solar cells without anti-reflector coating is 7.0% under AM 1.5 at 25 
C. The samples were irradiated with electrons at 1 MeV at room temperature. The current-voltage characteristics under AM0 and the quantum efficiency (QE) were measured before and after irradiations. Electron irradiation effects on single junction GaAs solar cells fabricated under the same process were also studied for comparison. The value of QE for both the GaAs solar cells with and without QD layers slightly decreases due to the irradiation at 110
/cm, and no remarkable decrease in the increment of the QE in a long wavelength region due to the existence of QDs is observed.
Oshima, Takeshi; Sato, Shinichiro; Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*
no journal, ,
Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi; Sugaya, Takeyoshi*
no journal, ,
no abstracts in English
Nakamura, Tetsuya*; Sumita, Taishi*; Imaizumi, Mitsuru*; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*; Mochizuki, Toru*; Takeda, Akihiro*; Okano, Yoshinobu*; Sato, Shinichiro; et al.
no journal, ,
Radiation effects on GaAs solar cells with InGaAs dot layers were investigated in order to consider the capability of them for space applications. The GaAs solar cells with 50 InGaAs dot layers and also GaAs solar cells with no dot layer were fabricated using a MBE method. They were irradiated with 150 keV-protons at room temperature. As a result, solar cell with dot layers showed higher radiation degradation in short circuit current however, lower degradation in open circuit voltage. Since no significant difference in the degradation of current - voltage characteristics under dark conditions between dot and non-dot solar cells, it is concluded that the degradation of fill fuctor does not come from the degradation of pn diode characteristics but might come from the degradation of minority carrier diffusion length.
Oshima, Takeshi; Nakamura, Tetsuya*; Sugaya, Takeyoshi*; Sumita, Taishi*; Imaizumi, Mitsuru*; Sato, Shinichiro; Matsubara, Koji*; Niki, Shigeru*; Mochizuki, Toru*; Takeda, Akihiro*; et al.
no journal, ,
Oshima, Takeshi; Nakamura, Tetsuya*; Sumita, Taishi*; Imaizumi, Mitsuru*; Sato, Shinichiro; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*; Mochizuki, Toru*; Okano, Yoshinobu*
no journal, ,
Sato, Shinichiro; Oshima, Takeshi; Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*; Takeda, Akihiro*; Okano, Yoshinobu*
no journal, ,
no abstracts in English
