摘要
Recent experiments suggest graphene-based materials as candidates for use in future electronic and optoelectronic devices.In this study,we propose a new multilayer quantum dot(QD)superlattice(SL)structure with graphene as the core and silicon(Si)as the shell of QD.The Slater-Koster tight-binding method based on Bloch theory is exploited to investigate the band structure and energy states of the graphene/Si QD.Results reveal that the graphene/Si QD is a type-I QD and the ground state is 0.6 eV above the valance band.The results also suggest that the graphene/Si QD can be potentially used to create a sub-bandgap in all Si-based intermediate-band solar cells(IBSC).The energy level hybridization in a SL of graphene/Si QDs is investigated and it is observed that the mini-band formation is under the infuence of inter-dot spacing among QDs.To evaluate the impact of the graphene/Si QD SL on the performance of Si-based solar cells,we design an IBSC based on the graphene/Si QD(QDIBSC)and calculate its short-circuit current density(J_(sc))and carrier generation rate(G)using the 2D fnite diference time domain(FDTD)method.In comparison with the standard Si-based solar cell which records J_(sc)=16.9067 mA/cm^(2)and G=1.48943×10^(28)m^(−3)⋅s^(−1),the graphene/Si QD IBSC with 2 layers of QDs presents Jsc=36.4193 mA/cm^(2)and G=7.94192×10^(28)m^(−3)⋅s^(−1),ofering considerable improvement.Finally,the efects of the number of QD layers(L)and the height of QD(H)on the performance of the graphene/Si QD IBSC are discussed.
