Ultrafast photocarrier transport dynamics in InAs/GaAs quantum dot superlattice solar cell

We studied time-resolved carrier transport through InAs/GaAs quantum dot superlattice (QDSL) solar cells, using time-of-flight spectroscopy with an optical probe structure lying beneath the QDSL. The density of photoexcited carriers in the top p-GaAs layer significantly influences the time-resolved photoluminescence (TRPL) of probe while TRPL of QDSL keeps unchanged. Also, the PL intensity of probe showed exponential increase as the excitation pulse energy increased, which may indicate that the dynamics of holes rule the dynamics observed in TRPL. The induced filling of QD states by strong excitation leads to the condition where carries travel over the QDSL and reach the probe faster.