EDXD under solar illumination (EDXD)

EDXD under solar illumination

Barbara Paci -

Rome - Tor Vergata

Energy-dispersive X-ray spectroscopy is an analytical technique for characterizing materials. It differs from conventional X-ray spectroscopy by using polychromatic photons as the source and is usually operated at a fixed angle. It differs from conventional X-ray spectroscopy in the use of a polychromatic beam as a probe and because the working geometry is at fixed angle, with no need of a goniometer. The advantages of the ED mode are that it acquires at fixed scattering angle, it works directly in reciprocal space, collection time is faster and data collection is simultaneous. The fixed scattering angle geometry makes this technique especially suitable for in situ studies in special environments. This apparatus, for example, has been integrated with a transparent sample holder and a solar simulator thus allowing the study in real time of photoactive materials during lighting. Although the technique has a lower resolution due to the solid state detector (lower precision), it is possible to obtain a high accuracy measurement of the lattice parameters given the very high reproducibility of the spectra over time (there are no movements therefore the same sample portion is always observed) and allows for rapid structural analysis.

TECHNICAL SPECIFICATIONS

Siefert 3.5KW Generator: typical working conditions E=55kV, I=40mA max.
X-Ray sources with W and Ag anode
ORTEC Ge-Single crystal solid state detector
ORTEC-ADCAM Electronic data acquisition
In House acquisition software
Motorized arms, max 25°for each arm
W collimation slits (square or rectangular collimation) : max collimation 20*20m μm
Manual and motorized translators (x-y)
Standard sample holder
Especially designed sample holder for Joint X-ray/Solar simulator measurements: Transparent quartz holder
Integrated LOT AM1.5 Solar simulator

AVAILABLE TECHNIQUES

In situ time resolved EDXD
Joint EDXD/solar illumination
In situ time resolved Joint EDXD/solar illumination

SAMPLE

Thin films max in plane dimensions 8cm*8cm.
Multilayered samples max in plane dimensions 8cm*8cm.

USE FOR

Determining structural parameters and phases of films/multilayers.
In situ time resolved monitoring of structural parameters and phases for thin films/multilayers as a function of external conditions: ambient conditions, controlled atmospheres, solar simulator exposure.
Primary and secondary crystallization/amorphization studies of thin films/multilayers in situ and time resolved.

Case Studies

In situ space-resolved X-ray diffraction and time-resolved EDXD on efficient polymer-based photovoltaic devices: Microstructural properties and aging effects

Microstructural and morphological features of the layers forming integrated PTB7/PC71BM organic solar cells with Ca/Al cathode are studied.
The effects of vacuum treatment on properties and durability were addressed. For this propose, time-resolved experiments revealing the structural evolution of the active layers under illumination were conducted combining the in situ energy dispersive X-ray diffraction (EDXD) technique with atomic force microscopy (AFM).

See: F. Silvestri et al. Journal of Materials Research 2017 , pp. 1969-1981

Enhanced Structural Stability and Performance Durability of Bulk Heterojunction Photovoltaic Devices Incorporating Metallic Nanoparticles

It is shown, for the first time, that the incorporation of Ag nanoparticles P3HT:PCBM bulk heterojunction (BHJ) leads to improved structural and morphological properties of the composite BHJ solar cells and to better photovoltaic (PV) stability after long periods of continuous illumination. This is evidenced by an original approach based on joint X-ray/AFM monitoring, combined with time-resolved energy dispersive X-ray diffraction (EDXD) and electrical measurements. It can be postulated that the incorporation of metallic nanoparticles in the BHJ leads to a dual enhancement, a plasmon absorption mediated effect, causing improved initial cell efficiency, and a structural stability effect giving rise to reduced degradation rate upon prolonged illumination. The results are in favor of the exploitation of polymer–nanoparticle composites as a promising approach to mitigate the aging effects in OPVs

See: B. Paci et all Adv. Funct. Mater. 2011, 21, 3573–3582

EDXD under solar illumination (EDXD)