Engineering topics

Norman, Andrew (ORCID:000000016368521X)

Publications and source records attributed to Norman, Andrew (ORCID:000000016368521X).

4 records

DOE OSTI2023

Investigating Electric Field and Light Induced Degradation in Perovskite Solar Cells through Nanometer-Scale Potential Imaging

Electric field and light induced degradations in perovskite solar cells were evaluated through nanometer-scale potential imaging across the device by using in-situ Kelvin probe force microscopy (KPFM). We derived the electric field profile from potential profiles at different bias voltages to evaluate the locations and quality of junctions across the device. We found relative changes in electric field peak intensity at the HTL/perovskite and perovskite/ETL interfaces upon stressing devices separately under voltage or light. KPFM results during 12-hour stress/rest cycling under electrical bias show both reversible and irreversible changes in the device's interfacial fields. We also observed change in the electric field profile between control and degraded devices after 100 hours of stress/rest cycling under light. Our results demonstrate how nanometer-scale potential imaging can be used to understand the impacts of external electric fields and light soaking on both irreversible degradation and reversible metastability in perovskite solar cells.

Kelvin probe force microscopy↗

DOE OSTI2022

Nanoscale Three-Dimensional Imaging of Degradation in Composite Si-Containing Anodes

The use of silicon (Si) in next-generation lithium-ion battery (LIB) anodes has the potential to dramatically improve electrochemical performance over current LIB graphite (Gr) anodes, due to silicon’s higher specific capacity.1 However, widespread implementation of Si-containing anodes is inhibited by issues such as significant Si volume expansion during lithiation and an unstable solid-electrolyte interphase (SEI), resulting in unreliable performance and poor cycle life. Currently, composite anodes with both Si and graphite active materials are used to increase capacity and mitigate some of the limitations associated with Si. In composite electrodes with a heterogeneous distribution of components with varying electrical properties (including Si, Gr, conductive carbon additive, and binder), it is important to understand the local distribution of each component to correlate with electrochemical processes, particularly localized degradation and heterogeneous aging, and to optimize performance. To investigate Si-containing composite anodes in the nanoscale, we use scanning spreading resistance microscopy (SSRM), a form of scanning probe microscopy (SPM) that probes local electronic resistivity. By examining the intrinsic electronic resistivity contrast between the anode components, separate phases can be distinguished and understood within the composite structure.2 This work studies the effect of electrochemical cycling in two different electrolytes on component distribution and aging by comparing the electrical and structural evolution of composite Si-graphite electrodes and SEI before and after charge-discharge cycling. 1. W. J. Zhang. A review of the electrochemical performance of alloy anodes for lithium-ion batteries J. Power Sources 196 13–24 (2011). 2. C. Stetson, Z. Huey, A. Downard, Z. Li, B. To, A. Zakutayev, C.-S. Jiang, M. Al-Jassim, D. Finegan, S.-D. Han and S. DeCaluwe: Three-Dimensional Mapping of Resistivity and Microstructure of Composite Electrodes for Lithium-Ion Batteries. ACS Nano Letters Accepted (2020).

ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2022

Silicon Heterojunction Field Performance

The market share of silicon heterojunction (SHJ) modules are expected to increase in the following years. The presentation discusses field performance of SHJ and compares it to other high-efficiency modules. In-depth materials characterization is used to understand the origins of degradation in these type of modules.

ENGINEERING,SOLAR ENERGY↗

DOE OSTI2020

A Comparison of the Optoelectronic Properties of High-Efficiency Polycrystalline and Epitaxial Cu(In,Ga)Se2 Photovoltaic Films

Over the last several decades, champion photovoltaic (PV) devices using CuInGaSe2 (CIGS) as the absorber material have been achieved using polycrystalline films exclusively. This has led to the assumption that polycrystalline CIGS generally outperform single-crystal CIGS in PV devices. However, recently, very high-quality epitaxial CIGS has been grown on GaAs substrates producing PV device efficiencies of 20.0%. These results have revived the debate on what effects grain boundaries have on PV device efficiencies. In this contribution, we compare the optoelectronic properties of polycrystalline CIGS films with those of high-efficiency epitaxial CIGS films. This comparison reveals that grain boundaries are associated with properties that negatively impact PV device efficiency. Additionally, we find that the grain interiors in polycrystalline films exhibit properties that are similar to the high-performance epitaxial films. Our results suggest that it may be possible to achieve higher device efficiencies with epitaxial CIGS than with polycrystalline films.

41 EE - Solar Energy Technologies Office (EE-4S)↗