Device Band Diagrams vs Charge Transport Mechanisms: The CREM view of ETA Solar Cells

Sub-surface domains commonly play critical roles in the device performance. Yet, their characterization by any of the standard electrical tools is not easy; a direct consequence of the fact that it is always the integral volume between applied electrodes that is probed. 

A recent method, CREM (chemically resolved electrical measurements), can in principle address this major limitation.1,2 CREM exploits x-ray photoelectron spectroscopy (XPS) for the extraction of electrical properties in a non-contact mode and, most importantly, it proposes a unique capability: following the electrostatic potential variations at selected sub-surface domains. CREM application to gate oxides, molecular layers and photo-sensitive systems has already demonstrated marked achievements in the derivation of band diagrams and related junction-fields,3 domain-specific dielectric properties, challenging aspects of the charge dynamics and photo-activity, in particular.

Here, CREM of extremely thin absorber (ETA) solar cells will be described, together with a general review on the technique capabilities, its limitations and possible developmental improvements. Examples for the insight gained on fundamental questions and charge transport mechanisms will be given.

References:

1. H.Cohen, Appl. Phys. Lett. 85, 1271-3 (2004).

2. I. Doron Mor et al., Nature 406, 382-5 (2000).

3. Y. Itzhaik, G. Hodes, H. Cohen, J. Phys. Chem. Lett. 2, 2872-6 (2011).