Showing posts with label photovoltaic. Show all posts
Showing posts with label photovoltaic. Show all posts

April 24, 2019

Video: Analysis of techniques for measuring carrier recombination lifetime

Author:  Dr. Richard K. Ahrenkiel is a Research Professor of Metallurgical and Materials Engineering at the Colorado School of Mines in Golden, Colorado.


Rapid, accurate and contactless measurement of the recombination lifetime is a very important activity in photovoltaics. The excess carrier lifetime (Δn(t)) is the most critical and variable parameter in the development of photovoltaic materials. Device performance can be accurately predicted from the lifetime measurement of the starting material. However, there is no single measurement that directly measures the bulk lifetime as all measurements are based on a device model.

A primary issue is that the lifetime is a function of excess carrier lifetime, and measurements must be linked to an injection level. The most common measurements are based on either photoconductive (PCD) or photoluminescence (TRPL) decay. PC decay senses the product of excess carrier concentration (Δn) and mobility (μ (Δn)). This mobility variation must be included in order to extract the true excess carrier lifetime. TRPL works best for direct band gap materials and therefore is not applicable to silicon. For polycrystalline materials, shallow traps distort the measurement and must be included in the analysis of the data. Finally, surface and interface recombination have a profound influence on most measurements and must be minimized for accurate measurement of the true bulk lifetime.

Both techniques and analysis methods will be discussed in this seminar. Typical sample measurements will be shown, including representative thin film and wafer materials that are currently popular in the photovoltaic community.

Richard Keith Ahrenkiel (2013), "Analysis of Techniques for Measuring Carrier Recombination Lifetime,"

April 22, 2019

Review of the STARCELL project publications

 This project is developed in the European Union due to photovoltaics is one of the main technologies necessary to achieve the targets of EU Energy Roadmap 2050.  For me, it is interesting to know the state of the art of this material as a prospect for a postdoctoral stay in 2019-2020.

  • This topic is highly related to solar cell development and innovation.
  • One key feature is the development of thin film photovoltaics using flexible substrates

Webpage Snapshot (April 22nd, 2019) - STARCELL Project 

STARCELL aims to substitute two critical raw materials (In and Ga) used in conventional thin film photovoltaic (PV) technologies, via the introduction of sustainable kesterite (Cu
2ZnSn(S,Se)4 - CZTSSe) semiconductors. (Project STARCELL Objective)


[1] S. Giraldo, E. Saucedo, M. Neuschitzer, F. Oliva, M. Placidi, X. AlcobĂ©, V. Izquierdo-Roca, S. Kim, H. Tampo, H. Shibata, A. PĂ©rez-RodrĂ­guez, P. Pistor, How small amounts of Ge modify the formation pathways and crystallization of kesterites, Energy Environ. Sci. 11 (2018) 582–593. doi:10.1039/c7ee02318a. (Link)(Cited by 22)

[2] S.G. Haass, C. Andres, R. Figi, C. Schreiner, M. BĂĽrki, Y.E. Romanyuk, A.N. Tiwari, Complex Interplay between Absorber Composition and Alkali Doping in High-Efficiency Kesterite Solar Cells, Adv. Energy Mater. 8 (2018) 1–9. doi:10.1002/aenm.201701760. (Link) (Cited by 11)

[3] C.J. Hages, A. Redinger, S. Levcenko, H. Hempel, M.J. Koeper, R. Agrawal, D. Greiner, C.A. Kaufmann, T. Unold, Identifying the Real Minority Carrier Lifetime in Nonideal Semiconductors: A Case Study of Kesterite Materials, Adv. Energy Mater. 7 (2017) 1–10. doi:10.1002/aenm.201700167. (Link) (Cited by )

[4] J. Márquez, H. Stange, C.J. Hages, N. Schaefer, S. Levcenko, S. Giraldo, E. Saucedo, K. Schwarzburg, D. Abou-Ras, A. Redinger, M. Klaus, C. Genzel, T. Unold, R. Mainz, Chemistry and Dynamics of Ge in Kesterite: Toward Band-Gap-Graded Absorbers, Chem. Mater. 29 (2017) 9399–9406. doi:10.1021/acs.chemmater.7b03416. (Link