RESUMEN
By taking advantage of the outstanding intrinsic optoelectronic properties of perovskite-based photovoltaic materials, together with the strong near-infrared (NIR) absorption and electronic confinement in PbS quantum dots (QDs), sub-bandgap photocurrent generation is possible, opening the way for solar cell efficiencies surpassing the classical limits. The present study shows an effective methodology for the inclusion of high densities of colloidal PbS QDs in a MAPbI3 (methylammonium lead iodide) perovskite matrix as a means to enhance the spectral window of photon absorption of the perovskite host film and allow photocurrent production below its bandgap. The QDs were introduced in the perovskite matrix in different sizes and concentrations to study the formation of quantum-confined levels within the host bandgap and the potential formation of a delocalized intermediate mini-band (IB). Pronounced sub-bandgap (in NIR) absorption was optically confirmed with the introduction of QDs in the perovskite. The consequent photocurrent generation was demonstrated via photoconductivity measurements, which indicated IB establishment in the films. Despite verifying the reduced crystallinity of the MAPbI3 matrix with a higher concentration and size of the embedded QDs, the nanostructured films showed pronounced enhancement (above 10-fold) in NIR absorption and consequent photocurrent generation at photon energies below the perovskite bandgap.
RESUMEN
A natural pigment (Anthocyanin extracted from Sambucus nigra L. fruit) was incorporated by dipping sputtered titanium oxide films into a pigment solution. The pigment solution has red colour and an absorption peak located in the wavelength range of 520 to 540 nm. Titanium oxide thin films were prepared by reactive DC magnetron sputtering and reactive pulsing DC magnetron sputtering from a Titanium target in O2 + Ar atmosphere onto glass slides. Pigment incorporation in thin films was found dependent of both morphology and composition, which depends on deposition parameters, like pulsing frequency and oxygen flow rate. The incorporation of this pigment in TiOx thin films increases the final solar absorption and decreases the final average roughness of these films. The effect in solar absorption is higher in films prepared by DC and pulsed DC at pulsing frequency of 200 kHz.
