[20a-136-1~10] 13.9 Compound solar cells

△ [20a-136-10] Comparison of Effective Carrier Mobility between Wire on Well and Multiple Quantum Well by Time of Flight Measurement

〇Meita Asami¹, Kasidit Toprasertpong¹, Kentaroh Watanabe², Yoshiaki Nakano¹, Yoshitaka Okada^1,2, Masakazu Sugiyama^1,2 (1.Tokyo Univ., 2.RCAST)

Keywords:semiconductor, quantum well solar cells

The conventional triple junction solar cells which achieved the efficiency over 40%; however, it is known that the bandgap of the middle cell, GaAs, is not suitable to achieve the highest efficiency of the triple-junction solar cells. According to the calculation, it is known that the suitable bandgap of the middle cell is 1.20 eV, while the bandgap of the conventional second cell is 1.40 eV. We need the lattice-matched materials whose bandgap is 1.20 eV. One of the candidates is multiple quantum well (MQW). The carrier collection efficiency(CCE) of the MQW solar cells, however, is low due to the carrier confinement effect in quantum wells. We measured the effective mobility of the normal MQW and WoW(special MQW grown on off-oriented substrates) in order to investigate which structure is better to solve this CCE problem.