Princeton University

School of Engineering & Applied Science

How to assess operational stability of perovskite solar cells with reversible degradation?

Speaker: 
Professor Eugene Katz, Ben-Gurion University of the Negev, Israel
Location: 
Engineering Quadrangle, J401
Date/Time: 
Wednesday, November 15, 2017 - 1:30pm

Development of hybrid organic-inorganic halide perovskite solar cells (PSCs) combining high performance and operational stability is a key issue for implementation of this technology. Both reversible improvement and reversible degradation of PSC efficiency were previously reported under illumination-darkness cycling. Quantifying the performance and stability of cells exhibiting significant diurnal performance variation is challenging and requires specific protocols. In this talk I will discuss outdoor stability measurements of two types of devices showing either reversible photo-degradation or pronounced reversible efficiency improvement under sunlight-soaking. Analysis of the results suggests that the figures of merit for photovoltaic performance and stability of such devices should be reconsidered. Instead of the classical approach of reporting the initial (or stabilized) efficiency value and estimation of T80, we propose to use the value of energy output generated during the first day of the exposure (or first illumination period in the light/darkness cycling indoor) and the time needed for reaching its 20% drop, respectively. The latter accounts for both the long-term irreversible degradation and the reversible diurnal efficiency variation and does not depend on the type of processes prevailing in a given perovskite cell.

Possible underlying mechanisms for reversible, irreversible and apparently irreversable performance losses will be discussed on the basis of I-V curves evolution, transient electrical measurements and photoluminescence studies.