ABSTRACT
Although perovskite solar cells have achieved excellent photoelectric conversion efficiencies, there are still some shortcomings, such as defects inside and at the interface as well as energy level dislocation, which may lead to non-radiative recombination and reduce stability. Therefore, in this study, a double electron transport layer (ETL) structure of FTO/TiO2/ZnO/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD is investigated and compared with single ETL structures of FTO/TiO2/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD and FTO/ZnO/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD using the SCAPS-1D simulation software, with special attention paid to the defect density in the perovskite active layer, defect density at the interface between the ETL and the perovskite active layer, and temperature. Simulation results reveal that the proposed double ETL structure could effectively reduce the energy level dislocation and inhibit the non-radiative recombination. The increases in the defect density in the perovskite active layer, the defect density at the interface between the ETL and the perovskite active layer, and the temperature all facilitate carrier recombination. Compared with the single ETL structure, the double ETL structure has a higher tolerance for defect density and temperature. The simulation outcomes also confirm the possibility of preparing a stable perovskite solar cell.
ABSTRACT
Colloidal CdSe/ZnS quantum dots (QDs) exhibit excellent optical properties for wide potential applications in light-emitting diodes, solar concentrators, and single-photon sources. However, the ultra-thin films with low concentration of QDs still encounter inefficient photoluminescence (PL) and poor directionality of radiation, which need to be enhanced using nanophotonics device designs. Here we design and experimentally demonstrate an on-substrate silicon nitride (SiN) photonic crystal (PhC) microcavity encapsulated by a layer of PMMA hosting CdSe/ZnS QDs. The miniaturized bound states in the continuum (BIC) supported by our structures, provide high-Q resonant modes with highly-directional emission patterns. Experimental results show that the BIC mode in the microcavity has a Q-factor up to 7000 owing to the symmetric refractive index distribution along the Z-direction, rendering 8.5-fold enhancement of PL intensity and 8.4-fold acceleration of radiative emission rate. Our work provides a practical way for constructing efficient on-chip surface-emitting light sources on silicon-based integrated photonic devices.
