Tandem solar cell slide share
description
Transcript of Tandem solar cell slide share
J. Am. Chem. Soc., 2013, 135, 877
Synthesis of Ternary Cadmium Chalcogenides
Hot Injection Method
Se + S(in TOP)
Thermocouple
CdSeCdS
Gradient Structure:Formed due to higher reactivity of Se towards Cd compare to S
By changing the composition, i.e., Se to S ratio, the band gap of QDs can be tuned easily
Absorption Spectra Emission Spectra
Band gap can be tuned without changing the size of
the ternary QDs
Under UV light illumination
Photophysical Properties
Photographs of QDs dispersed in toluene under UV light illumination
Quantum Dot Solar Cell (QDSC)
Loading of QDs to mesoporous TiO2 film: Electrophoretic Deposition (EPD)
QDs are generally negatively charged in solution and can be driven towards an electrode by applying a potential
QDSCs are assembled in sandwich fashion Cu2S-Reduced graphene oxide (RGO) used
as counter electrode Aqueous polysulfide solution used as
electrolyte
CdSeS
Increasing Se:S
h 2.0% 2.4% 2.8%
With decreasing band gap, the power conversion efficiency goes up. This is due to absorption of light at higher wavelength
Quantum Dot Solar Cell (QDSC)
Can we still improve the efficiency? Possibly a new design!
Sequential vs. MixedEPD has the ability to load QDs sequentially
by choosing different solutions
Expt. Calc.Green + Red 2.49 1.91Orange + Red 3.20 2.27Green + Orange + Red 3.00 1.87Green, Orange and Red (mixed) 2.34 2.21
h (%)
Quantum Dot Solar Cell (QDSC)
Electron Transfer Energy Transfer
Two possible mechanism for the synergistic enhancement
Detailed time-resolved spectroscopic experiments are in progress to investigate the synergy
Quantum Dot Solar Cell (QDSC)
Highly luminescent ternary chalcogenides with gradient structure offers a new way to design QDSCs
EPD helps in forming layer-by-layer structure within mesoscopic TiO2 film, thus maximizes the light harvesting capability
Sequential ordering of higher-band-gap QDs followed by lower-band-gap QDs provides a better synergy for harvesting photons across visible spectrum
Conclusions
AcknowledgementsDivision of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, Office of Science, United States Department of Energy through Grant DE-FC02-04ER15533
Thank you for your attention!