Examinando por Autor "Climent-Pascual, Esteban"

Mostrando 1 - 3 de 3

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.
Huge Photo-Stability Enhancement in Bismuth Doped Methylammonium Lead Iodide Hybrid Perovskites by Light Induced Transformation
(ACS, 2019-04-26) Bartolomé, Javier; Climent-Pascual, Esteban; Redondo-Obispo, Carlos; Álvarez, Angel L; de Andrés, Alicia; Coya, Carmen
The doping strategy of hybrid perovskites is being extensively explored not only for higher efficiency but also to overcome issues in photovoltaic materials such as self-degradation pathways in an ambient atmosphere or under visible irradiation. Here, BiI3 is introduced in the synthesis of MAPbI3 films (MA: CH3–NH3+) to stabilize the material. Around 25% of nominal Bi3+ is accommodated in the perovskite structure, producing a shrinking of the unit cell and a small increase of the band gap. The presence of empty Bi gap states quenches the 770 nm red interband emission and results in a near-infrared emission at 1100 nm. However, high enough visible irradiation density induces a progressive segregation of Bi3+ out of the perovskite lattice and promotes the re-emergence of the red emission. This emission is blue-shifted, and its intensity increases strongly with time until it reaches a saturation value which remains stable in the transformed films for extremely high power densities, around 1000 times higher than for undoped samples. We propose that the underlying processes include the formation of BiI3 and BiOI, probably at the surface of the crystals, hampering the usual decomposition pathways into PbI2 and PbOx for undoped MAPbI3. These results provide a new path for obtaining highly stable materials which would allow an additional boost of hybrid perovskite-based optoelectronics.
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.