Colloidal PbS and PbSeS Quantum Dot Sensitized Solar Cells Prepared by Electrophoretic Deposition

Here we report the developement of quantum dot sensitized solar cells (QDSCs) using colloidal PbS and PbSeS QDs and polysulfide electrolyte for high photocurrents. QDSCs have been prepared in a novel sensitizing way employing electrophoretic deposition (EPD), and protecting the colloidal QDs from corrosive electrolyte with a CdS coating. EPD allows a rapid, uniform and effective sensitization with QDs, while the CdS coating stabilizes the electrode. The effect of electrophoretic deposition time and of colloidal QD size on cell efficiency is analyzed. Efficiencies as high as 2.1±0.2% are reported

Nanomorphology influence on the light conversion mechanisms in highly efficient diketopyrrolopyrrole based organic solar cells

In this work, diketopyrrolopyrrole-based polymer bulk heterojunction solar cells with inverted and regular architecture have been investigated. The influence of the polymer:fullerene ratio on the photoactive film nanomorphology has been studied in detail. Transmission Electron Microscopy and Atomic Force Microscopy reveal that the resulting film morphology strongly depends on the fullerene ratio. This fact determines the photocurrent generation and governs the transport of free charge carriers. Slight variations on the PCBM ratio respect to the polymer show great differences on the electrical behavior of the solar cell. Once the polymer:fullerene ratio is accurately adjusted, power conversion efficiencies of 4.7% and 4.9% are obtained for inverted and regular architectures respectively. Furthermore, by correlating the optical and morphological characterization of the polymer:fullerene films and the electrical behavior of solar cells, an ad hoc interpretation is proposed to explain the photovoltaic performance as a function of this polymer:blend composition

<span style="font-size: 22.5pt;mso-bidi-font-size:15.5pt;font-family:"Times New Roman","serif"; mso-bidi-font-weight:bold">Effect of preparation procedures on long-term performance of SnO_{<span style="font-size:17.5pt;mso-bidi-font-size:10.5pt; font-family:"Times New Roman","serif";mso-bidi-font-weight:bold">2</span>}<span style="font-size:17.5pt;mso-bidi-font-size:10.5pt;font-family:"Times New Roman","serif"; mso-bidi-font-weight:bold"> <span style="font-size:22.5pt;mso-bidi-font-size: 15.5pt;font-family:"Times New Roman","serif";mso-bidi-font-weight:bold">thin film sensing layers deposited with different methodologies </span></span></span>

749-766<span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">There is an increasing demand for SnO<span style="font-size:12.5pt; mso-bidi-font-size:5.5pt;font-family:" arial","sans-serif""="">2 semiconducting gas sensors for several monitoring applications that have sensitivity, selectivity and reliability on a long-term scale. The present paper reviews the long-term performance of SnO2 thin film sensing layers, which strongly depend on the preparation procedures and different thin film deposition techniques. <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">The stability and reliability are very important for tin dioxide based gas sensor devices, when these are to be integrated with standard CMOS circuitry. The stability in the output of the thin film sensing layer is very essential to implement reliable integrated sensor device, because a small drift in the baseline leads to a large change in the biasing current in the subsequent <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" times="" new="" roman","serif""="">signal processing circuit. The long-term stable behaviour of the SnO2 thin film gas sensor has been found in the literature, and it depends on the thin film deposition conditions, annealing temperature, time, ambient, and noble metal/metal oxide dopant. It can be seen from the literature that, sensitivity and stability of SnO<span style="font-size:13.0pt;mso-bidi-font-size: 6.0pt;font-family:" times="" new="" roman","serif""="">2 thin film were strongly affected with variation in the crystallite (grain) size and growth procedures. The thin films were deposited by chemical methods such as, screen-printing, sol-gel, spray pyrolysis, etc. and physical methods such as, RGTO, sputtering, PLA, etc. with the grain size varying from 5 to 50 nm with annealing temperatures varying in the range 500-800<span style="font-size:20.0pt; mso-bidi-font-size:13.0pt;font-family:" times="" new="" roman","serif""="">°C and with noble metal/metal oxide dopants. Such type treated SnO2 thin films have a little change in sensitivity but the sensing layer has much higher, long time operational stability. </span

Electrodeposition of Antimony Selenide Thin Films and Application in Semiconductor Sensitized Solar Cells

Sb₂Se₃ thin films are proposed as an alternative light harvester for semiconductor sensitized solar cells. An innovative electrodeposition route, based on aqueous alkaline electrolytes, is presented to obtain amorphous Sb₂Se₃. The amorphous to crystalline phase transition takes place during a soft thermal annealing in Ar atmosphere. The potential of the Sb₂Se₃ electrodeposited thin films in semiconductor sensitized solar cells is evaluated by preparing TiO₂/Sb₂Se₃/CuSCN planar heterojunction solar cells. The resulting devices generate electricity from the visible and NIR photons, exhibiting the external quantum efficiency onset close to 1050 nm. Although planar architecture is not optimized in terms of charge carrier collection, photocurrent as high as 18 mA/cm², under simulated (AM1.5G) solar light, is achieved. Furthermore, the effect of the Sb₂Se₃ thickness and microstructural properties on the photocurrent is analyzed, suggesting the hole transport is the main limiting mechanism. The present findings provide significant insights to design efficient semiconductor sensitized solar cells based on advanced architectures (e.g., nanostructured and tandem), opening wide possibilities for progresses in this emerging photovoltaics technology

Passivation of ZnO Nanowire Guests and 3D Inverse Opal Host Photoanodes for Dye-Sensitized Solar Cells

A hierarchical host-guest nanostructured photoanode is reported for dye-sensitized solar cells. It is composed of ZnO nanowires grown in situ into the macropores of a 3D ZnO inverse opal structure, which acts both as a seed layer and as a conductive backbone host. Using a combination of self-assembly, hydrothermal or electrodeposition of single crystalline ZnO nanowires and TiO2 passivation, a novel photoanode with scattering capability for optimal light harvesting is fabricated. © 2014 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

Naphthalimide end-capped diphenylacetylene: a versatile organic semiconductor for blue light emitting diodes and a donor or an acceptor for solar cells

A novel compound 6,6′-(ethyne-1,2-diylbis(4,1-phenylene))bis(2-(2-butyloctyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione) (NAI-PVP-NAI) based on an end capping group 1,8-naphthalimide and central building block diphenylacetylene was designed and synthesized by Suzuki coupling. The newly synthesized NAI-PVP-NAI compound is characterized using optical, thermal, and electrochemical techniques as well as ab initio modeling. This novel and unique compound exhibits strong blue emission in the solid state and has been successfully used as an active light-emitting layer in organic light emitting diodes (OLEDs). Interestingly, the newly developed compound shows both electron-donating and electron-accepting abilities. Therefore, it can act as a donor or an acceptor organic semiconductor. Indeed, upon evaluating this molecule in solution processable organic photovoltaic (OPV) devices, we show that it acts as a donor when used with a PCBM acceptor and as an acceptor when used with a P3HT donor. Thus, NAI-PVP-NAI is a versatile compound, which can play three roles as a blue light emitting layer in OLEDs and a donor or an acceptor in OPV devices.</p

Organo-metal halide perovskite-based solar cells with CuSCN as the inorganic hole selective contact

CuSCN is proposed as a cost-competitive hole selective contact for the emerging organo-metal halide perovskite-based solar cells. The CuSCN films have been deposited by a solution casting technique, which has proven to be compatible with the perovskite films, obtaining planar-like heterojunction-based glass/FTO/TiO2/CH3NH3PbI3−xClx/CuSCN/Au solar cells with a power conversion efficiency of 6.4%. Among the photovoltaic parameters, the fill factor (i.e. 62%) suggests good carrier selectivity and, therefore, efficient functionality of the TiO2 and CuSCN charge carrier selective contacts. However, the open-circuit voltage (Voc), which remains low in comparison with the state of the art perovskite-based solar cells, appears to be the main limiting parameter. This is attributed to the short diffusion length as determined by impedance spectroscopy. However, the recombination losses are not only affected by the CuSCN, but also by the perovskite film. Indeed, variations of 20 °C in the thermal annealing of the perovskite films result in changes larger than 200 mV in the Voc. Furthermore, a detailed analysis of the quantum efficiency spectra contributes significant insights into the influence of the selective contacts on the photocurrent of the planar heterojunction perovskite solar cells

Colloidal PbS and PbSeS Quantum Dot Sensitized Solar Cells Prepared by Electrophoretic Deposition

Here we report the development of quantum dot sensitized solar cells (QDSCs) using colloidal PbS and PbSeS quantum dots (QDs) and polysulfide electrolyte for high photocurrents. QDSCs have been prepared in a novel sensitizing way employing electrophoretic deposition (EPD) and protecting the colloidal QDs from corrosive electrolyte with a CdS coating. EPD allows a rapid, uniform, and effective sensitization with QDs, while the CdS coating stabilizes the electrode. The effect of electrophoretic deposition time and of colloidal QD size on cell efficiency is analyzed. Efficiencies as high as 2.1 ± 0.2% are reported

Short alkyl chain engineering modulation on naphthalene flanked diketopyrrolopyrrole toward high-performance single crystal transistors and organic thin film displays

Studying multi-purpose applications of a specific material is a challenging topic in the organic electronics community. In this work, through molecular engineering and smart device structure design strategy, high performance in transistors and thin film display devices is simultaneously achieved by applying a simple new dye molecule, naphthalene flanked diketopyrrolopyrrole (DPPN), as the active layer material. Short alkyl chains (hexyl or octyl side groups for H-DPPN and O-DPPN, respectively) are adapted to improve the hole mobility in organic thin film transistors (OTFTs) and single crystal transistors (SCTs). Specifically, H-DPPN shows a similar hole mobility in either OTFTs or SCTs, while O-DPPN exhibits a dramatically enhanced mobility, reaching 0.125 cm2 V−1 s−1 in SCTs. Additionally, a smart organic light emitting diode (OLED) device is designed by using DPPN molecule as the dopant with a host matrix. The promising external quantum efficiencies of 4.0% and 2.3% are achieved for H-DPPN and O-DPPN fabricated OLEDs. Overall, in this work, it is reported that DPP-based small molecules can simultaneously function well in both transistors and thin film displays with high device performance through molecular and smart device engineering.</p