| 1. |
- Gao, Yijun, et al.
(författare)
-
Enhancing PbS Colloidal Quantum Dot Tandem Solar Cell Performance by Graded Band Alignment
- 2019
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 10:19, s. 5729-5734
-
Tidskriftsartikel (refereegranskat)abstract
- Colloidal quantum dot solids are attractive candidates for tandem solar cells because of their widely tunable bandgaps. However, the development of the quantum dot tandem solar cell has lagged far behind that of its single-junction counterpart. One of the fundamental problems with colloidal quantum dot solar cells is the relatively small diffusion length, which limits the quantum dot absorbing layer thickness and hence the power conversion efficiency. In this research, guided by optical modeling and utilizing a graded band alignment strategy, a two-terminal monolithic solution-processed quantum dot tandem solar cell has been successfully fabricated and a power conversion efficiency of 6.8% has been achieved. The band grading approach utilized the complementary tuning of work functions and band alignment through judicious choices of the nanoparticle surface chemistry and quantum dot confined size. This work demonstrates a general approach to improving the efficiency for tandem thin-film solar cells.
|
|
| 2. |
- Limpert, Steven, et al.
(författare)
-
Absorption in and scattering from single horizontal Au-contacted InAs/InP heterostructure nanowires
- 2016
-
Ingår i: 16th International Conference on Numerical Simulation of Optoelectronic Devices, NUSOD 2016. - 9781467386036 ; , s. 221-222
-
Konferensbidrag (refereegranskat)abstract
- Finite element modelling (FEM) is used to show that the addition of Au contacts to a single horizontal InAs/InP heterostructure nanowire substantially alters the nanowire's optical properties in comparison to the uncontacted case. It is found that the addition of contacts can increase absorption efficiency, decrease scattering efficiency and shift the location of absorption within the nanowire. Localized surface plasmon resonances are found to develop at nanowire/contact interfaces at infrared wavelengths and contribute to the alteration of the optical response of the nanowire.
|
|
| 3. |
- Limpert, Steven, et al.
(författare)
-
Bipolar Photothermoelectric Effect Across Energy Filters in Single Nanowires
- 2017
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 17:7, s. 4055-4060
-
Tidskriftsartikel (refereegranskat)abstract
- The photothermoelectric (PTE) effect uses nonuniform absorption of light to produce a voltage via the Seebeck effect and is of interest for optical sensing and solar-to-electric energy conversion. However, the utility of PTE devices reported to date has been limited by the need to use a tightly focused laser spot to achieve the required, nonuniform illumination and by their dependence upon the Seebeck coefficients of the constituent materials, which exhibit limited tunability and, generally, low values. Here, we use InAs/InP heterostructure nanowires to overcome these limitations: first, we use naturally occurring absorption "hot spots" at wave mode maxima within the nanowire to achieve sharp boundaries between heated and unheated subwavelength regions of high and low absorption, allowing us to use global illumination; second, we employ carrier energy-filtering heterostructures to achieve a high Seebeck coefficient that is tunable by heterostructure design. Using these methods, we demonstrate PTE voltages of hundreds of millivolts at room temperature from a globally illuminated nanowire device. Furthermore, we find PTE currents and voltages that change polarity as a function of the wavelength of illumination due to spatial shifting of subwavelength absorption hot spots. These results indicate the feasibility of designing new types of PTE-based photodetectors, photothermoelectrics, and hot-carrier solar cells using nanowires.
|
|
| 4. |
- Limpert, Steven, et al.
(författare)
-
Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage
- 2017
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 28:43
-
Tidskriftsartikel (refereegranskat)abstract
- Compared to traditional pn-junction photovoltaics, hot carrier solar cells offer potentially higher efficiency by extracting work from the kinetic energy of photogenerated 'hot carriers' before they cool to the lattice temperature. Hot carrier solar cells have been demonstrated in high-bandgap ferroelectric insulators and GaAs/AlGaAs heterostructures, but so far not in low-bandgap materials, where the potential efficiency gain is highest. Recently, a high open-circuit voltage was demonstrated in an illuminated wurtzite InAs nanowire with a low bandgap of 0.39 eV, and was interpreted in terms of a photothermoelectric effect. Here, we point out that this device is a hot carrier solar cell and discuss its performance in those terms. In the demonstrated devices, InP heterostructures are used as energy filters in order to thermoelectrically harvest the energy of hot electrons photogenerated in InAs absorber segments. The obtained photovoltage depends on the heterostructure design of the energy filter and is therefore tunable. By using a high-resistance, thermionic barrier, an open-circuit voltage is obtained that is in excess of the Shockley-Queisser limit. These results provide generalizable insight into how to realize high voltage hot carrier solar cells in low-bandgap materials, and therefore are a step towards the demonstration of higher efficiency hot carrier solar cells.
|
|
| 5. |
- Ren, Dingding, et al.
(författare)
-
Single-Mode Near-Infrared Lasing in a GaAsSb-Based Nanowire Superlattice at Room Temperature
- 2018
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:4, s. 2304-2310
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductor nanowire lasers can produce guided coherent light emission with miniaturized geometry, bringing about new possibilities for a variety of applications including nanophotonic circuits, optical sensing, and on-chip and chip-to-chip optical communications. Here, we report on the realization of single-mode and room-temperature lasing from 890 to 990 nm, utilizing a novel design of single nanowires with GaAsSb-based multiple axial superlattices as a gain medium under optical pumping. The control of lasing wavelength via compositional tuning with excellent room-temperature lasing performance is shown to result from the unique nanowire structure with efficient gain material, which delivers a low lasing threshold of ∼6 kW/cm2 (75 μJ/cm2 per pulse), a lasing quality factor as high as 1250, and a high characteristic temperature of ∼129 K. These results present a major advancement for the design and synthesis of nanowire laser structures, which can pave the way toward future nanoscale integrated optoelectronic systems with superior performance.
|
|
