Measurement of ion beam induced current in quantum dot solar cells

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.

Comparative study on degradation characteristics of component subcells in IMM triple-junction solar cells irradiated with high-energy electrons and protons

Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Tajima, Michio*; Sato, Shinichiro; Oshima, Takeshi

Proceedings of 39th IEEE Photovoltaic Specialists Conference (PVSC-39) (CD-ROM), p.3243 - 3248, 2013/06

https://doi.org/10.1109/PVSC.2013.6745143

Radiation response of InGaP, GaAs, InGaAs (In=20%) and InGaAs (In=30%) single-junction solar cells, which are the component sbcells of IMM3J cells, were comparatively studied. High-energy electrons (1 MeV) and protons (10 MeV) were irradiated to the four types of the cells. The InGaP cell has the highest radiation resistance to both electrons and protons amongst the four cells as expected. On the other hand, the InGaAs cells have less resistant for Isc compared to InGaP and GaAs cells. However, the resistance of Voc of InGaAs cells is comparable to that of the other two cells. As a general result, InGaAs cells have less radiation resistance to electrons, while they have the resistance against protons equivalent to GaAs cell. These radiation response properties of InGaAs cells are thought to be useful to design radiation resistant IMM3J space solar cells.

Change in the electrical performance of GaAs solar cells with InGaAs quantum dot layers by electron irradiation

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

https://doi.org/10.1016/j.solmat.2012.09.027

GaAs solar cells which have a PiN structure with 50 self-organized InGaAs Quantum Dot (QD) layers were irradiated with 1 MeV electrons up to 110 /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.

Change in I-V characteristics of subcells in a multi-junction solar cell due to radiation irradiation

Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi

Proceedings of 38th IEEE Photovoltaic Specialists Conference (PVSC-38) (CD-ROM), p.002846 - 002850, 2012/00

https://doi.org/10.1109/PVSC.2012.6318183

Roensch et al. recently proposed a new method of estimating the current-voltage (IV) characteristics of subcells in a multi-junction (MJ) solar cell by using electroluminescence (EL). The estimated IV characteristics of a proton-irradiated MJ solar cell from the IV curve obtained from each subcell agreed well with the actual dark IV (DIV) and light IV (LIV) characteristics, except for series resistance () and shunt resistance (). This method can also clarify of a MJ cells and Rsh of subcells through circuit simulation program. In this work, we applied this method to InGaP/GaAs dual-junction (2J) solar cells in order to obtain the IV characteristics of the InGaP top subcells and GaAs bottom subcells before and after proton irradiation with various fluences. In addition, we succeeded to predict the degradation curve of maximum power () of the 2J solar cell where the current-limiting subcell changes from InGaP to GaAs subcell.

Radiation degradation of the electrical performance of InGaAs quantum dot solar cells and its recovery at room temperature

Oshima, Takeshi; Sato, Shinichiro; Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*

no journal, , 

Development and vision of super-high efficiency flexible space solar cells

Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Sato, Shinichiro; Oshima, Takeshi

no journal, , 

no abstracts in English

Effects on radiation tolerance of quantum dot layers in GaAs solar cells

Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sato, Shinichiro; Oshima, Takeshi; Sugaya, Takeyoshi*

no journal, , 

no abstracts in English

Radiation response of fill-factor for GaAs solar cells with InGaAs quantum dot layers

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.

Comparison of radiation response of component subcells in IMM triple-junction solar cells irradiated with electrons and protons

Imaizumi, Mitsuru*; Nakamura, Tetsuya*; Oshima, Takeshi

no journal, , 

no abstracts in English

Proton irradiation degradation of GaAs solar cells with InGaAs quantum dot layers

Sato, Shinichiro; Oshima, Takeshi; Nakamura, Tetsuya*; Imaizumi, Mitsuru*; Sugaya, Takeyoshi*; Matsubara, Koji*; Niki, Shigeru*; Takeda, Akihiro*; Okano, Yoshinobu*

no journal, , 

no abstracts in English