Quantum-Dot Intermediate-band Solar Cell used as Bottom Cell
Lin Zhu1,2,3, Yuji Hazama2,3, Changsu Kim2,3, Hidefumi Akiyama2,3
1Institute for Solar Energy Systems, Sun Yat-sen University, GuangZhou, China
/2Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
/3AIST-UTokyo OPERANDO-OIL, University of Tokyo, Kashiwa, Japan

 We discuss an advantage of using a quantum-dot (QD) intermediate band solar cell (IBSC) as a bottom cell in a 4-terminal tandem solar cell instead of a conventional bulk bottom cell. We introduce a parameter yCI = 1 – 0.001 to represent a slow or fast conduction-band-to-dots non-radiative relaxation rate, which correspond to strong or weak phonon-bottleneck effect. When a QD IBSC is used as a bottom cell, and is combined with a GaAs top cell, the QD cell exhibit efficiency boost of 1-2% than a conventional bulk bottom cell in the ideal case. Even for a QD bottom cell with yCI