Victor S. Balderrama

Nanoporous Anodic Alumina Barcodes: Toward Smart Optical Biosensors

Toward a smart optical biosensor based on nanoporous anodic alumina (NAA): by modifying the pore geometry in nanoporous anodic alumina we are able to change the effective medium at will and tune the photoluminescence of NAA. The oscillations in the PL spectrum are converted into exclusive barcodes, which are useful for developing optical biomedical sensors in the UV-Visible region.

Tunable Fabry-Pérot interferometer based on nanoporous anodic alumina for optical biosensing purposes

Here, we present a systematic study about the effect of the pore length and its diameter on the specular reflection in nanoporous anodic alumina. As we demonstrate, the specular reflection can be controlled at will by structural tuning (i.e., by designing the pore geometry). This makes it possible to produce a wide range of Fabry-Pérot interferometers based on nanoporous anodic alumina, which are envisaged for developing smart and accurate optical sensors in such research fields as biotechnology and medicine. Additionally, to systematize the responsiveness to external changes in optical sensors based on nanoporous anodic alumina, we put forward a barcode system based on the oscillations in the specular reflection.

Organic Solar Cells Toward the Fabrication Under Air Environment

In this work, we analyze the performance parameters of the inverted organic solar cells (OSC) partially fabricated under an air environment, comparing them with those of similar solar cells manufactured totally under a nitrogen environment. Both solar cells use PTB7 and PC70BM as the active blend layer. The electrical parameters were extracted from the current density-voltage characteristic (J-V) under light and dark conditions. At the beginning, the OSCs partially fabricated under an air environment showed a similar performance as those manufactured under an N2 environment. After 120 h, the power conversion efficiency of the OSCs partially fabricated under an air environment decreased 32% with respect to its initial value. The degradation process under the ISOS-D1 protocols was also analyzed.

Influence and relationship of film morphology on Organic Solar Cells manufactured with different P3HT:PC [70] BM blend solutions

In the present work, the morphology and performance of Bulk Heterojunction Organic Solar Cells (BHJ-OSC) manufactured with three different ratios of P3HT:PC[70]BM (1∶0.84, 1∶1 and 1∶1.21, wt%) were studied. These films were made with a mixture of solvents o-dichlorobenzene:chlorobenzene (DCB:CB) at a fixed ratio by volume of 6∶4, v/v. The film morphology of the OSCs was characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The performance parameters of the OSC were extracted from current density-voltage characteristic (J-V) curves recorded in the dark and under illumination and correlated to the morphology of the active layer. We discuss observed variations in phase segregation regions due to changes in the P3HT:PC[70]BM ratio.

Impact of inkjet printed ZnO electron transport layer on the characteristics of polymer solar cells

In this paper, we demonstrate that zinc oxide (ZnO) layers deposited by inkjet printing (IJP) can be successfully applied to the low-temperature fabrication of efficient inverted polymer solar cells (i-PSCs). The effects of ZnO layers deposited by IJP as electron transport layer (ETL) on the performance of i-PSCs based on PTB7-Th:PC70BM active layers are investigated. The morphology of the ZnO-IJP layers was analysed by AFM, and compared to that of ZnO layers deposited by different techniques. The study shows that the morphology of the ZnO underlayer has a dramatic effect on the band structure and non-geminate recombination kinetics of the active layer deposited on top of it. Charge carrier and transient photovoltage measurements show that non-geminate recombination is governed by deep trap states in devices made from ZnO-IJP while trapping is less significant for other types of ZnO. The power conversion efficiency of the devices made from ZnO-IJP is mostly limited by their slightly lower JSC, resulting from non-optimum photon conversion efficiency in the visible part of the solar spectrum. Despite these minor limitations their J–V characteristics compare very favourably with that of devices made from ZnO layer deposited using different techniques.

High-efficiency organic solar cells based on a halide salt and polyfluorene polymer with a high alignment-level of the cathode selective contact

Advances in organic photovoltaic technology for improving the power conversion efficiency (PCE) towards the theoretical maximum require efficient light-absorbing polymers, a high alignment-level of selective contacts, and an easy manufacturing process with low cost to reach them. The halide salts constitute a highly promising class of materials that can produce better selective contacts in solar cells for improving the PCE. In this article, we demonstrate and report the use of a haloid salt in organic solar cells utilized as an interlayer. The haloid salt is deposited on top or below of polyfluorene polymer (PFN) layer and after it is placed on a transparent conductive oxide (TCO). Thermal evaporation of LiF layers is carried out to deposit ultrathin films of 0.5 nm to 0.8 nm thickness. As a photoactive layer we use the low-bandgap PBDTTT-EFT:PC70BM bulk-heterojunction. Among the different architectures analyzed we obtained a PCE of 11.00%, with an outstanding fill factor of FF = 73.5%, which is among the best reported for solar cells. This new stacking of a halide salt with polyfluorene materials could find use in fully exploiting the potential of various halide systems, and also opens up new opportunities to improve OSCs with a view to achieving record efficiencies.

Performance parameters degradation of inverted organic solar cells exposed under solar and artificial irradiance, using PTB7:PC 70 BM as active layer

In this work, the degradation of inverted bulk heterojunction organic solar cells (BHJ-OSC) exposed under solar and under artificial irradiance conditions is studied. The photovoltaic devices were based on the polymer PTB7 and the fullerene PC70BM and partially fabricated under air environment. The current density-voltage (J-V) characteristics of the devices were obtained at room temperature, under both dark and illumination conditions for a period of up to 1344 h. The samples were stored, between measurements, in a glove box under nitrogen environment.

Effect of variations in blend preparation on the properties of P3HT:PCBM blend solar cells

Polymeric solar cells have attracted much attention during the last years due to their lower fabrication cost and possibility of using flexible substrates. However, their efficiency is still less than 5%. Among factors affecting solar cells efficiency, the active layer morphology related to blend preparation and annealing, is one of the most important. In this work we analyze the behavior of solar cells based on P3HT:PCBM blends prepared under different conditions. Basic parameters are extracted from measured characteristics in dark and under illumination. Modeling is used to understand mechanisms involved in the device behavior and during its degradation, when working in ambient conditions.