Quantum Dot Solar Cells. Semiconductor Nanocrystals as Light Harvesters
18 Oct 2008-Journal of Physical Chemistry C (American Chemical Society)-Vol. 112, Iss: 48, pp 18737-18753
TL;DR: In this paper, three major ways to utilize semiconductor dots in solar cell include (i) metal−semiconductor or Schottky junction photovoltaic cell, (ii) polymer−smiconductor hybrid solar cell, and (iii) quantum dot sensitized solar cell.
Abstract: The emergence of semiconductor nanocrystals as the building blocks of nanotechnology has opened up new ways to utilize them in next generation solar cells. This paper focuses on the recent developments in the utilization of semiconductor quantum dots for light energy conversion. Three major ways to utilize semiconductor dots in solar cell include (i) metal−semiconductor or Schottky junction photovoltaic cell (ii) polymer−semiconductor hybrid solar cell, and (iii) quantum dot sensitized solar cell. Modulation of band energies through size control offers new ways to control photoresponse and photoconversion efficiency of the solar cell. Various strategies to maximize photoinduced charge separation and electron transfer processes for improving the overall efficiency of light energy conversion are discussed. Capture and transport of charge carriers within the semiconductor nanocrystal network to achieve efficient charge separation at the electrode surface remains a major challenge. Directing the future resear...
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TL;DR: In this paper, a quantum dot sensitizer layer can charge up to levels that alter the relative energetics within the cell thus affecting both the generation and recombination mechanisms, leading to new understanding of the photoelectrochemical mechanisms in quantum dot-sensitized solar cells.
Abstract: New results of photoelectrochemical solar cells that consist of quantum dots (QDs) deposited directly onto FTO glass identify chemical potential within the QD layer as the source for the observed photovoltage. Charge extraction and transient photovoltage measurements of this cell quantify the lifetime and density of the photogenerated electrons within the QDs layer. At open circuit voltage, the electron density approaches 1 × 1019/cm3, which corresponds to one electron per dot. The electron lifetime varies from 10 ms at low photovoltage to 0.1 ms at open circuit. These results lead to new understanding of the photoelectrochemical mechanisms in quantum dot sensitized solar cell. Under illumination, the QD sensitizer layer can charge up to levels that alter the relative energetics within the cell thus affecting both the generation and recombination mechanisms. The new insight, identifying a conceptual difference between QD and dye-sensitized solar cells, opens new paths for improvement and optimization of Q...
40 citations
TL;DR: In this article, the anatase TiO 2 nanoparticle films with different thicknesses have been fabricated through screen printing method, and CdS and cdSe quantum dots (QDs) have been deposited on TiO2 films in turn through successive ionic layer adsorption and reaction (SILAR) method.
40 citations
40 citations
TL;DR: In this article, a scalable photolithography process was used to construct bottom-gate and bottom-contact ambipolar PbS quantum dot thin-film-transistors (QD TFTs) with an electron/hole mobility of 0.47/0.43 cm2 V−1 s−1 and CMOS inverter circuits with gains of > 14 V at a supply bias of 10 V.
Abstract: Thiocyanate (SCN)-treated lead sulfide (PbS) quantum dot thin-film-transistors (QD TFTs) and CMOS-compatible circuits were fabricated on a flexible substrate via a scalable photolithography process. Spectroscopic and electrical investigations demonstrated that the thermal treatments induce ligand decomposition and densification of the QD arrays at around 170 °C. High temperature annealing above 200 °C induces an aggregation of the QD particles, resulting in a degradation of device performance, such as the field-effect mobility and the on-/off-current ratio. It is also noted that the surface defects which act as charge carrier traps are increased with the annealing temperature, possibly due to the decomposition of the SCN leading to an aggregation of the QD particles. On the basis of the experimental results, bottom-gate and bottom-contact ambipolar PbS QD TFTs with an electron/hole mobility of 0.47/0.43 cm2 V−1 s−1 and CMOS inverter circuits with gains of >14 V at a supply bias of 10 V were successfully fabricated on spin-on thin plastic substrates.
40 citations
16 Mar 2012
TL;DR: In this paper, the spectral losses in a single-junction semiconductor solar cell can be as large as 50% and the detailed balance limit of conversion efficiency for such a cell was determined to be 31%.
Abstract: The possibility to tune chemical and physical properties in nanosized materials has a
strong impact on a variety of technologies, including photovoltaics. One of the prominent
research areas of nanomaterials for photovoltaics involves spectral conversion.
Conventional single-junction semiconductor solar cells only effectively convert photons of
energy close to the semiconductor band gap (Eg) as a result of the mismatch between the
incident solar spectrum and the spectral absorption properties of the material (Green
1982, Luque and Hegedus 2003). Photons with an energy Eph smaller than the band gap
are not absorbed and their energy is not used for carrier generation. Photons with energy
Eph larger than the band gap are absorbed, but the excess energy Eph – Eg is lost due to
thermalization of the generated electrons. These fundamental spectral losses in a singlejunction
silicon solar cell can be as large as 50% (Wolf 1971), while the detailed balance
limit of conversion efficiency for such a cell was determined to be 31% (Shockley and
Queisser 1961). Several routes have been proposed to address spectral losses, and all of
these methods or concepts obviously concentrate on a better exploitation of the solar
spectrum, e.g., multiple stacked cells (Law et al. 2010), intermediate band gaps (Luque
and Marti 1997), multiple exciton generation (Klimov 2006, Klimov et al. 2007), quantum
dot concentrators (Chatten et al. 2003a) and down- and up-converters (Trupke et al. 2002a,
b), and down-shifters (Richards 2006a, Van Sark 2005). In general they are referred to as
Third or Next Generation photovoltaics (PV) (Green 2003, Luque et al. 2005, Marti and
Luque 2004). Nanotechnology is essential in realizing most of these concepts (Soga 2006,
Tsakalakos 2008), and semiconductor nanocrystals have been recognized as ‘building
blocks’ of nanotechnology for use in next generation solar cells (Kamat 2008). Being the
most mature approach, it is not surprising that the current world record conversion
efficiency is 43.5% for a GaInP/GaAs/GaInNAs solar cell (Green et al. 2011), although
this is reached at a concentration of 418 times.
40 citations
Cites background from "Quantum Dot Solar Cells. Semiconduc..."
...Nanotechnology is essential in realizing most of these concepts (Soga 2006, Tsakalakos 2008), and semiconductor nanocrystals have been recognized as ‘building blocks’ of nanotechnology for use in next generation solar cells (Kamat 2008)....
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References
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TL;DR: In this article, an upper theoretical limit for the efficiency of p−n junction solar energy converters, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of holeelectron pairs is radiative as required by the principle of detailed balance.
Abstract: In order to find an upper theoretical limit for the efficiency of p‐n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole‐electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction fc of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and fc as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000°K and 300°K, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and fc = 1. Actual junctions do not obey the predicted current‐voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.
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TL;DR: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects.
Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.
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TL;DR: In this paper, the carrier collection efficiency and energy conversion efficiency of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives.
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