ABSTRACT
In this work, we have experimentally investigated the impact of light trapping on the performance of InAs/GaAs quantum dot (QD) solar cells. To increase the amount of absorbed near-infrared photons, we fabricated a thin-film QD solar cell with a backside mirror where the positions of the QD layers were matched with the intensity peaks of one of the Fabry-Perot (FP) resonances in this structure to enable enhanced QD absorption near 1192 nm. We demonstrate that the external quantum efficiency at a given FP resonance wavelength of such an InAs/GaAs-based QD solar cell can be increased by an order of magnitude over solar cells without FP resonance by optimally positioning the QD layers.
ABSTRACT
A deep understanding of the effect of the A-site cation cross-exchange on the hot-carrier relaxation dynamics in perovskite quantum dots (PQDs) has profound implications on the further development of disruptive photovoltaic technologies. In this study, the hot carrier cooling kinetics of pure FAPbI3 (FA+ , CH(NH2 )2 + ), MAPbI3 (MA+ , CH3 NH3 + + ), CsPbI3 (Cs+ , Cesium) and alloyed FA0.5 MA0.5 PbI3 , FA0.5 Cs0.5 PbI3 , and MA0.5 Cs0.5 PbI3 QDs are investigated using ultrafast transient absorption (TA) spectroscopy. The lifetimes of the initial fast cooling stage (<1 ps) of all the organic cation-containing PQDs are shorter than those of the CsPbI3 QDs, as verified by the electron-phonon coupling strength extracted from the temperature-dependent photoluminescence spectra. The lifetimes of the slow cooling stage of the alloyed PQDs are longer under illumination greater than 1 sun, which is ascribed to the introduction of co-vibrational optical phonon modes in the alloyed PQDs. This facilitated efficient acoustic phonon upconversion and enhanced the hot-phonon bottleneck effect, as demonstrated by first-principles calculations.