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Sunday, February 10, 2019

#399 Graphene solar cells?

Recently, I came across a discussion regarding graphene solar cells. The term “graphene solar cell” implies the use of graphene as a material of which solar cell is constructed the same way inorganic (most notably silicon), organic semiconductors, or perovskite crystals are used (see earlier blogs). When used in this context, the term “graphene solar cells" seems to be somewhat misleading.

 

That is not to say there is no room for graphene in solar cells engineering. On the contrary, because of its distinct electrical, optical, and mechanical properties graphene is bound to play an important role in various solar cells, but rather as a part of the cell enabling its superior performance than the core material based on which cells are constructed. Whether in combination with other 2D materials (molybdenum disulfide MoS2 for instance), or with incorporation of graphene into the perovskite crystals, or with the use of graphene as a transparent, flexible contact material, there is no doubt graphene will serve various performance enhancing functions in solar cell technology. But should such cells be referred to as “graphene solar cells”? The term "graphene-based solar cells" seems to be better representing the concept of graphene use in solar cell engineering.

Posted by Jerzy Ruzyllo at 06:01 PM | Semiconductors | Link


Sunday, January 27, 2019

#398 Perovskite soiar cells

Since I’ve got into a brief overview of solar cells (see below), I cannot let it go without at least mentioning perovskite solar cells. Along with organic solar cells they represent emerging thin-film solar cell technology.

 

Perovskites are crystalline materials  chemical composition of which may vary significantly, but which feature the same crystal structure as calcium titanium oxide CaTiO3 (perovskite structure). They have very good solar light absorption characteristics (it means they use large portion of the solar light spectrum) and matured into cells featuring above 20% efficiency. Overall. perovskite solar cells  have a very good potential for low-cost large-scale commercialization.

 

In the case you are not all that familiar with perovskites check this site out. 

Posted by Jerzy Ruzyllo at 05:41 PM | Semiconductors | Link


Sunday, January 20, 2019

#397 SCST 16

Since 1989 I am involved in the organization of the International Symposium on Semiconductor Cleaning Science and Technology, SCST, under the auspicies of the Electrochemical Society. This time, symposium will be held during the ECS meeting in Atlanta, GA, Oct. 13-17, 2019.

 

Go to this site and check symposium G01 if interested in this topic. Or may be considering submitting an abstract? Abstarct submission site is now open

Posted by Jerzy Ruzyllo at 03:52 PM | Semiconductors | Link


Sunday, December 30, 2018

#396 2019

To all of you who visit this site, the very best wishes for the great New Year 2019!  Be on the lookout for the new entries coming out soon!

-JR

Posted by Jerzy Ruzyllo at 03:00 PM | Semiconductors | Link


Sunday, December 9, 2018

#395 It's IEDM time

Starting over ten years ago (see blog #5 posted in 2007) I like to remind you at this time of the year about IEDM (International Electron Device Meeting) which is a flagship semiconductor conference.

 

You may want to check the program of 2018 IEDM here.

Posted by Jerzy Ruzyllo at 03:13 AM | Semiconductors | Link


Sunday, November 4, 2018

#394 Organic solar cells

In the new generation photovoltaics special role is played by organic solar cells, or in other words, solar cells manufactured using organic semiconductors.

 

Organic solar cells are squarely at the other end of the efficiency paradigm than high-end solar cells solar cells mention earlier, but due to some unique features and low cost are bound to play a role on the photovoltaics arena.

 

Similarly to OLEDs (organic light-emitting diodes) the mechanism of light conversions into electricity is here somewhat different than in the case of inorganic semiconductor cells discussed earlier. In spite of the efficiency in the range of just few % in the basic version (efficiency increases even up to some 15% for more structurally complex configurations) and issues with stability when exposed to sunlight and elements, low-cost of organic cells combined with flexibility and transparency of the organic solar panels allows their uses in specialized applications where mostly rigid, opaque substrates based inorganic cells cannot be used.

 

See brief comments regarding perovskite solar cells which are in some ways similar to organic cells coming soon.

Posted by Jerzy Ruzyllo at 02:57 AM | Semiconductors | Link


Sunday, October 21, 2018

#393 High-end solar cells

As indicated earlier, silicon serves very well "mass photovoltaics". However, in order to meaningfully increase efficiency of solar cells, multi-junction, compound semiconductors-based cells known as tandem solar cells are being employed.

 

The goal is to improve the use the solar spectrum by stacking up semiconductors featuring different energy gaps in multi-junction cells arranged such that energy gap width increases from the bottom to the top of the stack. This arrangement assures absorption of the fairly broad range of wavelengths included in the solar spectrum with shortest being absorbed by the top layers and longer penetrating deeper into the stack where they are absorbed by the narrower bandgap materials. The result is high-cost class solar cells, but also the cells featuring the highest efficiencies approaching 50%.

Posted by Jerzy Ruzyllo at 12:34 PM | Semiconductors | Link


Sunday, September 16, 2018

#392 Silicon rules photovoltaics

In reference to the previous entry... Vast majority of solar cells is manufactured using silicon (in the order of decreasing efficiency either single-crystal, or multicrystalline, or amorphous depending on the needs) which is on one hand by far the most common and highly manufacturable semiconductor material, and on the other features energy gap which sufficiently well matches energy spectrum of the sunlight.

 

All in all, silicon very well serves the needs of photovoltaic industry and we are very lucky to have this outstanding element so readily available (sand!).

Posted by Jerzy Ruzyllo at 09:15 AM | Semiconductors | Link


Sunday, August 26, 2018

#391 Which solar cells where?

 As mentioned in previous entry, solar cells come in the variety of shapes. A question  is what type of cell is used where?

 

The choice is based on various criteria. For instance, what is the area available and how it defines the cost of the cells, and thus, materials/methods used to manufacture them? Is it a several square miles big part of the desert or few square meters wide satellite panel? Or maybe less than centimeter square cell powering a wrist watch or calculator?  In the first case cost is an issue because such a solar farm is meant to produce energy at the cost comparable with the energy obtained from other sources.  In the second case cost is not an issue because at whatever cost the highest efficiency solar cells must be used. In the third case the cost of the cell is marginal and is not even a consideration.

Posted by Jerzy Ruzyllo at 11:55 AM | Semiconductors | Link


Sunday, August 19, 2018

#390 Solar cells - efficiency

 Solar cells come in the broad range of material-device structure combinations. From elemental semiconductor  (silicon) to compound semiconductor based, from inorganic to organic semiconductors, from thin-film amorphous to single-crystal cells, from flexible to rigid, from low-cost to costly, ect. etc., performance of various classes of solar cells varies widly.

 

Parameter commonly used to describe performance of the solar cell  is its efficiency defined as a ratio of maximum power generated by the cell and the input power of the solar energy.  Efficiency of the solar cell is a function of material from which it is constructed and complexity of its structure, and thus, complexity of the processing steps employed in its manufacture. It can be as low as few % for the low-cost cells to close to 50% for the complex, multilayer cells. A universally valid rule is that the efficiency of solar cell is proportional to its cost which encompasses cost of the material used and cost of the manufacturing process.

  

Posted by Jerzy Ruzyllo at 03:13 PM | Semiconductors | Link


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Semi1source.com/blog is the personal blog of Jerzy Ruzyllo. With over 35 years of experience in academic research and teaching in the area of semiconductor engineering (currently holding position of a Distinguished Professor of Electrical Engineering and Professor of Materials Science and Engineering at Penn State University), he has a unique perspective on the developments in this progress driving technical domain and enjoys blogging about it.



With over 2000 terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today.






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