Examinando por Autor "Ripolles, Teresa S"

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Enhanced Nonlinear Optical Coefficients of MAPbI3 Thin Films by Bismuth Doping
(ACS, 2020-02-18) Redondo-Obispo, Carlos; Suárez, Isaac; Quesada, Sergio J; Ripolles, Teresa S; Martínez-Pastor, Juan P; Álvarez, Angel L; de Andrés, Alicia; Coya, Carmen
The poor photostability under ambient conditions of hybrid halide perovskites has hindered their recently explored promising nonlinear optical properties. Here, we show how Bi3+ can partially substitute Pb2+ homogeneously in the commonly studied MAPbI3, improving both environmental stability and photostability under high laser irradiation. Bi content around 2 atom % produces thin films where the nonlinear refractive (n2) and absorptive coefficients (β), which modify the refractive index (Δn) of the material with light fluence (I), increase up to factors of 4 and 3.5, respectively, compared to undoped MAPbI3. Higher doping inhibits the nonlinear parameters; however, the samples show higher fluence damage thresholds. Thus, these results provide a road map on how MAPbI3 can be engineered for practical cost-effective nonlinear applications by means of Bi doping, including optical limiting devices and multiple-harmonic generation into optoelectronics devices.
Enhanced stability and efficiency in inverted perovskite solar cells through graphene doping of PEDOT:PSS hole transport layer
(Elsevier, 2020) Redondo-Obispo, Carlos Daniel; Ripolles, Teresa S; Cortijo-Campos, Sara; Álvarez, Angel Luis; Climent-Pascual, Esteban; de Andrés, Alicia; Coya, Carmen
Poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) plays a relevant role in the device performance as hole extraction layer (HTL) of inverted perovskite solar cells. Here, we show a simple lowtemperature spin coating method for obtaining homogenous graphene-doped thin films of PEDOT:PSS with improved electrical conductivity without decreasing optical transmittance.Moreover, the crystallinity and stability in ambient conditions of the perovskite grown on it are enhanced. The hydrophobic character of graphene probably blocks undesirable reactions hampering degradation. By impedance spectroscopy it is demonstrated better charge extraction and reduction of recombination mechanisms at the doped-HTL/perovskite interface, resulting in improved photovoltaic parameters of the solar cell and greater stability at roomoperation conditions thus providing a simple and cost-effective method of preparing solar cells based on hybrid perovskites.
Interface Engineering in Perovskite Solar Cells by low concentration of PEAI solution in the antisolvent step
(Wiley, 2021-12-03) Ripolles, Teresa S; Serafini, Patricio; Redondo-Obispo, Carlos; Climent-Pascual, Esteban; Masi, Sofía; Mora-Seró, Ivan; Coya, Carmen
In spite of the outstanding properties of metal halide perovskites, its polycrystalline nature induces a wide range of structural defects that results in charge losses that affect the final device performance and stability. Herein, a surface treatment is used to passivate interfacial vacancies and improve moisture tolerance. A functional organic molecule, phenylethyl ammonium iodide (PEAI) salt, is dissolved with the antisolvent step. The additive used at low concentration does not induce formation of low-dimensional perovskites species. Instead, the organic halide species passivate the surface of the perovskite and grain boundaries, which results in an effective passivation. For sake of generality, this facile solution-processed synthesis was studied for halide perovskite with different compositions, the standard perovskite MAPbI3, and double cation perovskites, MA0.9Cs0.1PbI3 and MA0.5FA0.5PbI3, increasing the average photoconversion efficiency compared to the reference cell by 18%, 32%, and 4% respectively, observed for regular, n-i-p, and inverted, p-i-n, solar cell configurations. This analysis highlights the generality of this approach for halide perovskite materials in order to reduce nonradiative recombination as observed by impedance spectroscopy.