Iron Pyrite Nanocrystal Back Contact for CdTe Solar Cells


Project ID:  D2014-32



Photovoltaic (PV) cells have been produced with a wide variety of materials for each functional layer. The typical PV is a substrate layer coated with a semiconductor layer and two ohmic contacts. Thin film solar cells use a thin absorbing layer, such as Cadmium telluride (CdTe). CdTe is the most eco-friendly, high efficiency, low cost PV, with the shortest energy payback time. Development of a stable and efficient back contact determines the long-term stability of the solar cells. Back contacts are typically made of materials containing copper, gold, zinc, aluminum, etc. Copper is commonly used, but results in degradation due to diffusion to the CdTe junction and often reduces performance of the solar cell. Therefore, there is a need for a back contact that allows a longer lifespan for solar cells.


Invention Description

Researchers at University of Toledo have developed an iron pyrite back contact for CdTe solar cells.  The back contact layer is configured as an ohmic contact containing an iron pyrite nanocrystal film that is directly in contact with the semi-conductive layer. This technology’s energy levels were found to best match with the CdTe. Importantly, the back contact does not diffuse and degrade the CdTe junction, extending the life and efficiency of the solar cell. The film can be fabricated via direct solution-deposition and does not require thermal processing to achieve a good quality contact



•       CdTe solar cells and potentially other PV technology



•       Prevents degradation caused by diffusion

•       Consistent performance and longer life span of solar cells

•       Earth abundant materials that are non-toxic

•       Inexpensive synthesis using solution based-method, can be fabricated at room temperature


IP Status:       Patent pending, US20160351736A1


1. K. P. Bhandari, P. J. Roland, T. Kinner,a Y. Cao, H. Choi, S. Jeong, and R. J. Ellingson.  "Analysis and characterization of iron pyrite nanocrystals and nanocrystalline thin films derived from bromide anion synthesis."  J. Mat. Chem. A 3, 6853-6861 (2015).  [ DOI: 10.1039/c4ta06320a ]

2.  Khagendra P. Bhandari, Prakash Koirala, Naba R. Paudel, Rajendra R. Khanal, Adam B. Phillips, Yanfa Yan, Robert W. Collins, Michael J. Heben, and Randy J. Ellingson.  "Iron pyrite nanocrystal film serves as a copper-free back contact for polycrystalline CdTe thin film solar cells."  Solar Energy Materials and Solar Cells 117, 108-114 (2015).

3. K. P. Bhandari, X. Tan, P. Zereshki, R. W. Collins, R. J. Ellingson.  "CdTe solar cells with iron pyrite thin film back contacts fabricated by a hybrid sputtering/co-evaporation process."  43rd IEEE Photovoltaic Specialists Conference (PVSC), 1425-1428 (2016).

4. Khagendra P. Bhandari,  Xinxuan Tan,  Peymon Zereshki,  Fadhil K. Alfadhili,

Adam B. Phillips, Prakash Koirala, Michael J. Heben,  Robert W. Collins, Randy J. Ellingson.  "Thin film iron pyrite deposited by hybrid sputtering/co-evaporation as a hole transport layer for sputtered CdS/CdTe solar cells."  Solar Energy Mat. and Solar Cells (2017) 163, 277-284.  DOI:10.1016/j.solmat.2017.01.044

Patent Information:
For Information, Contact:
Katherine Pollard
Licensing Associate
The University of Toledo
Randall Ellingson
Rajendra Khanal
Khagendra Bhandari
Back Contact
Solar cell