6 research outputs found
Highly Bendable Flexible Perovskite Solar Cells on a Nanoscale Surface Oxide Layer of Titanium Metal Plates
We report highly
bendable and efficient perovskite solar cells (PSCs) that use thermally
oxidized layer of Ti metal plate as an electron transport layer (ETL).
The power conversion efficiency (PCE) of flexible PSCs reaches 14.9%
with a short-circuit current density (<i>J</i><sub>sc</sub>) of 17.9 mA/cm<sup>2</sup>, open-circuit voltage (<i>V</i><sub>oc</sub>) of 1.09, and fill factor (ff) of 0.74. Moreover, the
Ti metal-based PSCs exhibit a superior fatigue resistance over indium
tin oxide/polyÂ(ethylene terephthalate) substrate. Flexible PSCs maintain 100% of their initial PCE even
after PSCs are bent 1000 times at a bending radius of 4 mm. This excellent
performance of flexible PSCs is due to high crystalline quality and
low oxygen vacancy concentration of TiO<sub>2</sub> layer. The concentration
of oxygen vacancies in the oxidized Ti metal surface controls the
electric function of TiO<sub>2</sub> as ETL of PSCs. A decrease in
the oxygen vacancy concentration of the TiO<sub>2</sub> layer is critical
to improving the electron collection efficiency of the ETL. Our results
suggest that Ti metal-based PSCs possess excellent mechanical properties,
which can be applied to the renewable energy source for flexible electronics
Depleted Bulk Heterojunctions in Thermally Annealed PbS Quantum Dot Solar Cells
We have studied the detailed interface
structure and energy conversion
behavior of TiO<sub>2</sub>/PbS heterojunction solar cells. Nanoscale
structure and composition analysis have revealed that thermal annealing
causes intermixing of the TiO<sub>2</sub> and PbS phases and influences
the morphologies and optical properties of the heterojunction film.
This intermixing increased the junction area within the depleted bulk
heterojunction (DBH) layer and promoted the carrier extraction from
PbS QDs to TiO<sub>2</sub>. In addition, the thermal annealing caused
interparticle necking between PbS QDs and increased the crystallinity
of the PbS QD film. Compared with unannealed PbS/TiO<sub>2</sub> heterojunction
solar cells, the formation of the DBH layer and the partial sintering
of PbS QDs led to a doubling of the short-circuit current (<i>J</i><sub>sc</sub>) and an improved energy conversion efficiency,
by 39%. Electric force microscopy analysis confirmed the presence
of a DBH layer. The electron lifetime and fill factor (FF) of the
solar cells decreased when the TiO<sub>2</sub>/PbS mixed film was
thermally annealed, and this was assigned to a lower recombination
resistance in the DBH layer. Post-treatment of PbS/TiO<sub>2</sub> DBH films with ethanedithiol was found to increase the recombination
resistance at PbS/TiO<sub>2</sub> interface and to enhance the energy
conversion efficiency to ∼4%
Additional file 1: Figure S1. of Room Temperature Deposition of Crystalline Nanoporous ZnO Nanostructures for Direct Use as Flexible DSSC Photoanode
J–V curves for four different ZnO electrodes with different dye and solution combination in 2 h sensitizing time. Figure S2. (a) J–V curves of DSSCs fabricated with nanostructured ZnO photoanodes as a function of dye adsorption time at 50 °C (all films were deposited under 300 mTorr and the thicknesses of all films were fixed to be 6.7 μm) and (b) as function of sample aging after fabrication. Table S1. Device parameters of dye-sensitized ZnO nanostructured photoanodes under simulated AM 1.5 G light illumination (a) as a function of dye adsorption time at 50 °C (the thicknesses of the films were fixed to be 6.7 μm) and (b) as function of sample aging after fabrication. Table S2. Dye loading of DSSCs fabricated with nanostructured ZnO photoanodes deposited under different ambient oxygen pressures. The thickness of the photoanodes was fixed to be 10 μm. Table S3. Statistical analysis of device parameters for five different DSSCs fabricated with nanostructured ZnO photoanodes deposited by PLD using the optimized condition. Figure S3. J–V curves of five different DSSCs fabricated with nanostructured ZnO photoanodes deposited by PLD using the optimized condition. Figure S4. The incident photon-to-current conversion efficiency (IPCE) spectrum of a DSSC with a nanostructured ZnO photoanode deposited under 300 mTorr by PLD. Figure S5. J–V curves of 300 mTorr 5-μm ZnO photoanodes deposited by PLD using PLD coupled with Pt/ITO/PEN flexible substrate. (DOCX 226 kb
Novel Carrier Doping Mechanism for Transparent Conductor: Electron Donation from Embedded Ag Nanoparticles to the Oxide Matrix
A trade-off between the carrier concentration
and carrier mobility is an inherent problem of traditional transparent
conducting oxide (TCO) films. In this study, we demonstrate that the
electron concentration of TCO films can be increased without deteriorating
the carrier mobility by embedding Ag nanoparticles (NPs) into Al-doped
ZnO (AZO) films. An increment of Ag NP content up to 0.7 vol % in
the AZO causes the electron concentration rising to 4 × 10<sup>20</sup> cm<sup>–3</sup>. A dependence of the conductivity
on temperature suggests that the energy barrier for the electron donation
from Ag NPs at room temperature is similar to the Schottky barrier
height at the Ag–AZO interface. In spite of an increase in
the electron concentration, embedded Ag NPs do not compromise the
carrier mobility at room temperature. This is evidence showing that
this electron donation mechanism by Ag NPs is different from impurity
doping, which produces both electrons and ionized scattering centers.
Instead, an increase in the Fermi energy level of the AZO matrix partially
neutralizes Al impurities, and the carrier mobility of Ag NP embedded
AZO film is slightly increased. The optical transmittance of mixture
films with resistivity less than 1 × 10<sup>–3</sup> Ω·cm
still maintains above 85% in visible wavelengths. This opens a new
paradigm to the design of alternative TCO composite materials which
circumvent an inherent problem of the impurity doping
Indium–Tin–Oxide Nanowire Array Based CdSe/CdS/TiO<sub>2</sub> One-Dimensional Heterojunction Photoelectrode for Enhanced Solar Hydrogen Production
For photoelectrochemical (PEC) hydrogen
production, low charge
transport efficiency of a photoelectrode is one of the key factors
that largely limit PEC performance enhancement. Here, we report a
tin-doped indium oxide (In<sub>2</sub>O<sub>3</sub>:Sn, ITO) nanowire
array (NWs) based CdSe/CdS/TiO<sub>2</sub> multishelled heterojunction
photoelectrode. This multishelled one-dimensional (1D) heterojunction
photoelectrode shows superior charge transport efficiency due to the
negligible carrier recombination in ITO NWs, leading to a greatly
improved photocurrent density (∼16.2 mA/cm<sup>2</sup> at 1.0
V vs RHE). The ITO NWs with an average thickness of ∼12 μm
are first grown on commercial ITO/glass substrate by a vapor–liquid–solid
method. Subsequently, the TiO<sub>2</sub> and CdSe/CdS shell layers
are deposited by an atomic layer deposition (ALD) and a chemical bath
deposition method, respectively. The resultant CdSe/CdS/TiO<sub>2</sub>/ITO NWs photoelectrode, compared to a planar structure with the
same configuration, shows improved light absorption and much faster
charge transport properties. More importantly, even though the CdSe/CdS/TiO<sub>2</sub>/ITO NWs photoelectrode has lower CdSe/CdS loading (i.e.,
due to its lower surface area) than the mesoporous TiO<sub>2</sub> nanoparticle based photoelectrode, it shows 2.4 times higher saturation
photocurrent density, which is attributed to the superior charge transport
and better light absorption by the 1D ITO NWs
Reduced Graphene Oxide/Mesoporous TiO<sub>2</sub> Nanocomposite Based Perovskite Solar Cells
We report on reduced graphene oxide
(rGO)/mesoporous (mp)-TiO<sub>2</sub> nanocomposite based mesostructured
perovskite solar cells that show an improved electron transport property
owing to the reduced interfacial resistance. The amount of rGO added
to the TiO<sub>2</sub> nanoparticles electron transport layer was
optimized, and their impacts on film resistivity, electron diffusion,
recombination time, and photovoltaic performance were investigated.
The rGO/mp-TiO<sub>2</sub> nanocomposite film reduces interfacial
resistance when compared to the mp-TiO<sub>2</sub> film, and hence,
it improves charge collection efficiency. This effect significantly
increases the short circuit current density and open circuit voltage.
The rGO/mp-TiO<sub>2</sub> nanocomposite film with an optimal rGO
content of 0.4 vol % shows 18% higher photon conversion efficiency
compared with the TiO<sub>2</sub> nanoparticles based perovskite solar
cells