CdTe Photovoltaics for Sustainable Electricity Generation AMIT MUNSHI 1,2 and WALAJABAD SAMPATH 1 1.—NSF Next Generation Photovoltaics Center, Colorado State University, Fort Collins, CO, USA. 2.—e-mail: munshiamit1985@gmail.com Thin ﬁlm CdTe (cadmium telluride) is an important technology in the devel- opment of sustainable and affordable electricity generation. More than 10 GW of installations have been carried out using this technology around the globe. It has been demonstrated as a sustainable, green, renewable, affordable and abundant source of electricity. An advanced sublimation tool has been devel- oped that allows highly controlled deposition of CdTe ﬁlms onto commercial soda lime glass substrates. All deposition and treatment steps can be per- formed without breaking the vacuum within a single chamber in an inline process that can be conveniently scaled to a commercial process. In addition, an advanced cosublimation source has been developed to allow the deposition of ternary alloys such as Cd x Mg 1x Te to form an electron reﬂector layer which is expected to address the voltage deﬁcits in current CdTe devices and to achieve very high efﬁciency. Extensive materials characterization, including but not limited to scanning electron microscopy, transmission electron mi- croscopy, energy dispersive x-ray spectroscopy, high-resolution transmission electron microscopy and electron back-scatter diffraction, has been performed to get a better understanding of the effects of processing conditions on CdTe thin ﬁlm photovoltaics. This combined with computer modeling such as den- sity function theory modeling gives a new insight into the mechanism of CdTe photovoltaic function. With all these efforts, CdTe photovoltaics has seen great progress in the last few years. Currently, it has been recorded as the cheapest source of electricity in the USA on a commercial scale, and further improve- ments are predicted to further reduce the cost while increasing its utilization. Here, we give an overview of the advantages of thin ﬁlm CdTe photovoltaics as well as a brief review of the challenges that need to be addressed. Some fun- damental studies of processing conditions for thin ﬁlm CdTe are also pre- sented along with fabrication conditions using the closed-space sublimation method. Key words: Cadmium telluride, thin ﬁlm, photovoltaics, sustainable energy, solar cells, chalcogen INTRODUCTION CdTe (cadmium telluride) photovoltaics is an important technology for the production of utility- scale affordable and sustainable electricity genera- tion. Recently, the price of electricity from a CdTe solar installation was US$0.0387/kWh, 1 which is signiﬁcantly lower than the average price of elec- tricity. With recent improvements, research-scale small devices have recorded efﬁciencies of 21.5% 2 while commercial modules with up to 18.6% 3 efﬁ- ciency have been produced. CdTe is a p-type absorber that has a band gap of 1.45 eV which is nearly optimum for photovoltaic conversion. It also has a high coefﬁcient of absorption which implies that a very thin ﬁlm (2 lm) 4,5 is enough to absorb most of the visible solar spectrum. However, ques- tions related to the toxicity of Cd, the availability of Te (Received October 8, 2015; accepted March 22, 2016) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-016-4484-7 Ó 2016 The Minerals, Metals & Materials Society