20 percent efficiency on less than 100 um thick industrieally feasible c-Si solar cells (20plus)


The overall objective of the current project is a significant contribution to the dissemination of PV in order to improve the sustainability of the European energy supply and to strengthen the situation of the European PV industry.br The approach to reach this overall objective is the development of solar cells which are substantially thinner than today’s common practice. We will reduce the current solar cell thickness of typically 180 µm down to a minimum of 50 µm. At the same time we target to produce solar cells with high efficiencies in the range of 20% light conversion rate into power. The processes will be optimized and transferred into a pilot production line aimingbr at an efficiency of 19.5% on wafers of 100 µm thickness at a yield that is comparable to the one in standard production lines. This shall help to drive down production costs significantly and save Si resources from today’s 8 grams per watt to 3 grams per watt.br In more detail the following topics are addressed: Wafering from Si ingots, surface passivation, light trapping, solar cell and module processing and handling of the thin wafers. br The partners of this project form an outstanding consortium to reach the project goals, including four leading European R&D institutes as well as four companies with recorded and published expertise in the field of thin solar cells and modules and handling of such. The project is structured in 10 work packages covering the process chain from wafer to module and the transfer into pilot production already at mid term as well as integral eco-assessment and management tasks.

  • WG Hahn (Photovoltaics)
    Terheiden, Barbara; Ballmann, Tabitha; Horbelt, Renate; Schiele, Yvonne; Seren, Sabine; Ebser, Jan; Hahn, Giso (2015): Manufacturing 100-µm-thick silicon solar cells with efficiencies greater than 20% in a pilot production line Physica Status Solidi (A) : Applications and Materials Science. 2015, 212(1), pp. 13-24. ISSN 0031-8965. eISSN 1521-396X. Available under: doi: 10.1002/pssa.201431241

Manufacturing 100-µm-thick silicon solar cells with efficiencies greater than 20% in a pilot production line


Reducing wafer thickness while increasing power conversion efficiency is the most effective way to reduce cost per Watt of a silicon photovoltaic module. Within the European project 20 percent efficiency on less than 100-µm-thick, industrially feasible crystalline silicon solar cells (“20plµs”), we study the whole process chain for thin wafers, from wafering to module integration and life-cycle analysis. We investigate three different solar cell fabrication routes, categorized according to the temperature of the junction formation process and the wafer doping type: p-type silicon high temperature, n-type silicon high temperature and n-type silicon low temperature. For each route, an efficiency of 19.5% or greater is achieved on wafers less than 100 µm thick, with a maximum efficiency of 21.1% on an 80-µm-thick wafer. The n-type high temperature route is then transferred to a pilot production line, and a median solar cell efficiency of 20.0% is demonstrated on 100-µm-thick wafers.

Origin (projects)

    Schiele, Yvonne; Book, Felix; Seren, Sven; Hahn, Giso; Terheiden, Barbara (2012): Screen-printed Al-alloyed rear junction solar cell concept applied to very thin (100 μm) large-area n-type Si wafers Energy Procedia. 2012, 27, pp. 460-466. ISSN 1876-6102. eISSN 1876-6102. Available under: doi: 10.1016/j.egypro.2012.07.094

Screen-printed Al-alloyed rear junction solar cell concept applied to very thin (100 μm) large-area n-type Si wafers


Reducing the thickness of crystalline Si wafers processed to solar cells returns two significant benefits. Firstly, processing cost is reduced by saving cost- and energy-intensive Si material. Secondly, the required diffusion length of minority carriers is smaller, thus, wafers with a smaller carrier lifetime (e.g. due to higher base doping) can be utilized. In this work, the industrially feasible "PhosTop" cell concept is employed by manufacturing large-area n-type rear junction solar cells with a screen-printed Al-alloyed emitter featuring a selective phosphorous front surface field and a SiO2/SiNx passivation on the front.
PC1D simulations for substrates with different base doping concentrations show that the range of base resistivities utilizable for those PhosTop solar cells is extended towards higher doping concentrations with decreasing wafer thickness. PC1D forecasts a conversion efficiency of the chosen 2.8 Ωcm n-type Czochralski-Si wafers of 19.2% for 100 μm thickness, merely 0.1% less than for standard thickness but saving ∼25% of the Si material. The manufactured thin large-area solar cells achieve a maximum efficiency of 19.0%.

Origin (projects)

Funding sources
Name Finanzierungstyp Kategorie Project no.
Europäische Union third-party funds research funding program 638/10
Further information
Period: 01.10.2010 – 30.09.2013