1. Increasing desire for renewable energy sources has led to the rapid growth and development of photovoltaic (PV) technologies within the last few decades. It is estimated that 3,850,000 exajoules (10 18 joules) in the form of light is received by the earth per year, and the goal of photovoltaics is to harness this energy for use by converting it to electrical power. Advances in PV technology allow for higher efficiencies, increasing the viability and the presence of photovoltaics in the world. Yaroslaw Bagriy and Tyler Denis 5/7/14

2.  Definitions  Efficiency  Materials and Approaches  Worldwide Statistics and Applications  Advantages and Disadvantages  Summary  References  Key Concepts

3.  Photovoltaics  Solar radiation to direct electrical current  Generations  First – pn junction  Second – Thin film  Third - Multilayer  Production  Deposition  Lattice Matching  Nominal Power  Watt-peak, Wp http://www.liv.ac.uk/media/livacuk/renewableenergy/images/pvfig3.gif Basic pn junction solar cell operation

4.  The efficiency of a solar cell is defined as the ratio of output electrical power to incident optical power.  Solar constant: ~1.36 kW/m 2

5. http://www.nrel.gov/ncpv/images/efficiency_chart.jpg

6.  Layering of materials  Multiple bandgaps  III-V tandems http://www.sciencedirect.com/scie nce/article/pii/S136970210770278X http://www.nrel.gov/pv/multijunction.html

7.  Perovskite Video Perovskite Video http://cen.acs.org/articles/92/i8/Tapping-Solar-Power-Perovskites.html “On right, a SEM shows the layered structure of a research type organo lead trihalide perovskite solar cell. On left, a graphic shows how charge moves across these layers.”

8.  Low Concentration PV (LCPV)  2 – 100 suns  Medium Concentration PV  100 – 300 suns  High Concentration PV (HCPV)  300+ suns, 500 to 1000 suns are typical  Multijunction cells have a lower temperature coefficient than silicon  Compensates for increased cost of multijunction cells

9. Right - http://www.solarfeeds.com/wp-content/uploads/2013/02/cpv-solfocus.jpg Left - http://www.greenerideal.com/wp-content/uploads/2012/12/amonix-CPV-modules.jpg Amonix CPV Array

10. All images from Solar3D, http://www.solar3d.com/technology.php The 3D structure “traps” and reflects photons, increasing the probability of generating an electron-hole pair. This allows for a wider angle of incident light. Produced on silicon, and is therefore cheap and very cost effective. SEM image of 3D photovoltaic structure

11. Source: http://www.solar3d.com/technology.php

12. Source: EPIA Market Report 2013

13. Source: http://en.wikipedia.org/wiki/Renewable_energy

14.  Advantages  Once manufactured, photovoltaic cells produce pollution- free energy.  Costs of mass production are decreasing as performance is increasing compared to other energy sources.  Efficiencies are quickly increasing; projections indicate that higher efficiencies will soon be met.  Disadvantages  The sun is not always shining; alternative methods are required to store energy.  Can be very expensive to produce advanced photovoltaic cells.  Must be maintained to prevent degradation of performance (dust build up, cell failure, etc.).

15.  There are many methods of producing photovoltaic cells and the technology, and therefore the efficiency, is rapidly increasing.  Advances in photovoltaics are not solely based on new materials but also new methods of producing photovoltaics.  The biggest issue with solar power generation is the storage of energy when sunlight is not present.

16.  Jacoby, Mitch. "Tapping Solar Power With Perovskites." CEN RSS. C&EN, 24 Feb. 2014. Web. 04 May 2014..  Conibeer, Gavin. "Third-generation Photovoltaics." Third-generation Photovoltaics. MaterialsToday, Nov. 2007. Web. 04 May 2014..  "Technology." Solar3D. Solar3D, 2010. Web. 04 May 2014..  "Market Report 2013." EPIA. European Photovoltaic Industry Association, 2013. Web. 4 May 2014..  "NREL: Photovoltaics Research Home Page." NREL: Photovoltaics Research Home Page. N.p., n.d. Web. 04 May 2014..

17.  The goal of advanced photovoltaics is to increase the efficiency of converting solar energy into usable electrical energy.  Increasing the number of energy levels by adding more layers of materials will increase the chances of producing electron-hole pairs.  A 3D photovoltaic structure allows for light to generate electricity at wider angles.  By concentrating light onto a small multijunction cell, the solar constant (optical power) is increased.  The greatest issue with photovoltaics is currently with storing the energy that is produced.