NM05.08.16 : Solution-Processed Nanocrystal Based Thin Films as Hole Transport Materials in Cadmium Telluride Photovoltaics

5:00 PM–7:00 PM Apr 4, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Ebin Bastola1 Kamala KhanalSubedi1 Khagendra Bhandari1 Randy Ellingson1

1, University of Toledo, Toledo, Ohio, United States

The cadmium telluride (CdTe) photovoltaics is an efficient and cost-effective photovoltaic technology platform for harvesting solar energy. However, device efficiency remains limited in part by low-open circuit voltage (VOC) and fill factor (FF) due to inefficient transport of photo-generated charge carriers. Given the deep valence band of CdTe, the use of Cu/Au as a back contact serves primarily to narrow the width of the inherent Schottky evident in CdTe solar cells. (in our laboratory, copper/gold (Cu/Au) has been used as a standard back contact). For efficient transport of carriers to and into the back contact, a hole transport layer (HTL) is desired with valence band edge comparable to that of CdTe (~ -5.7 eV). Here, we report the solution-processed nanocrystal (NC) based thin films as HTLs in CdTe solar cells. The materials we discuss include the earth abundant iron pyrite (FeS2) NCs, nickel-alloyed iron pyrite (NixFe1-xS2) NCs, zinc copper sulfide (ZnxCu1-xS) nanocomposites, and perovskite based films. The FeS2 and NixFe1-xS2 NCs are synthesized by using hot-injection route, and then thin films are fabricated by drop-casting, and spin-coating techniques using colloidal NCs. ZnxCu1-xS thin films are fabricated by chemical bath deposition. These NC-based thin films are applied and studied as the HTLs in CdTe devices. On using these materials, the device performance increases by up to 10% compared to the standard Cu/Au back contact. We will discuss the benefits, challenges, and opportunities for these back contact materials in CdTe photovoltaics.