Bulletin of the American Physical Society
2018 Annual Fall Meeting of the APS Ohio-Region Section
Volume 63, Number 15
Friday–Saturday, September 28–29, 2018; University of Toledo, Toledo, Ohio
Session E02: Condensed Matter Physics III |
Hide Abstracts |
Chair: Kamala K. Subedi, The University of Toledo Room: SU 2584 |
Saturday, September 29, 2018 9:00AM - 9:15AM |
E02.00001: Cadmium Telluride Thin Film Solar Cells with Copper-Free, Low Barrier Back Contacts Fadhil K Alfadhili, Geethika K Liyanage, Jacob M Gibbs, Manoj K Jamarkattel, Adam B Phillips, Michael J. Heben Formation of a good back contact to CdTe thin film solar cell is a prime challenge due to the high work function of CdTe. Traditionally, Cu doping has been widely used to reduce the barrier between CdTe and back contact. However, Cu can fast diffuse into the main junction CdS/CdTe which is shunting the device over time. To overcome this, copper-free inorganic and organic buffer layers have been used as a back contact for CdTe devices such as Sb2Te3, As2Te3, MoOx, single-walled carbon nanotubes (SWCNTs), poly (3-hexylthiophene) (P3HT), and poly (3,4-ethyelenlenedioyyiohene): poly (styrene sulfonate) (PEDOT: PSS). Here, we demonstrate that by using layers of Te/ZnTe /Te at the back contact of CdTe without any intentional use of Cu. We found that the barrier height at the back of these Cu-free CdTe devices is lower than that of the CdTe devices with Cu/Au back contact, due to reduce band banding and the reduced carrier recombination at the back of the device, which leads to higher the open circuit voltage (VOC). |
Saturday, September 29, 2018 9:15AM - 9:30AM |
E02.00002: Impact of Selenium on Surface Morphology & Charge Carrier Dynamics of co-Sputtered CdSexTe1-x Alloys Niraj Shrestha, Corey Grice, Ebin Bastola, Khagendra Bhandari, Yanfa Yan, Randy J. Ellingson Band gap of the co-sputtered CdSexTe1-x ternary alloys for various concentration of Se has been calculated using absorbance and photoluminescence (PL) spectra. A clear evidence of band gap bowing with bowing parameter b = (0.81 ± 0.03) was observed consistent with the values reported by the previous researchers. Enhanced grain size and monotonic increase in photogenerated charge carrier lifetime with Se content has also been observed in CdSexTe1-x alloy. We attributed such a prolonged carrier lifetime to the shallowing of sub-gap defect states because of band gap narrowing, and the enlarged grain. |
Saturday, September 29, 2018 9:30AM - 9:45AM |
E02.00003: Glancing Angle Deposition: Effective Way of Controlling Optical and Microstructural Properties of Thin Films Dipendra Adhikari, Prakash Koirala, Maxwell Junda, Robert w. Collins, Nikolas Podraza Glancing angle deposition (GLAD) can be used to engineer different microstructures in thin films, resulting in wide variation in optical and micro-structural properties. GLAD using a sputter target at an oblique angle relative to the substrate normal can be used to produce columnar films tilted relative to the substrate normal. GLAD CdTe films sputtered on soda lime glass at room temperature with different source flux angle shows well defined columnar structures while films produced at 250°C only show variations in grain orientation. The dependence of grain size, grain orientation, in-plane stress, and optical properties of CdTe films on source flux angle are identified. Optical and microstructural properties of GLAD ITO and ZnO thin films deposited on soda lime glass at various source flux angles are also studied using SEM, XRD and spectroscopic ellipsometry. |
Saturday, September 29, 2018 9:45AM - 10:00AM |
E02.00004: Lost in Transition: VO2’s Wild Ride Maxwell M. Junda, P. B. Ribbon, Nikolas Podraza The semiconductor-to-metal transition (SMT), in addition to being an interesting phenomenon in its own right, is a highly useful effect that can be leveraged in switchable opto-electronic devices. Here we study the SMT exhibited by polycrystalline VO2 thin films deposited by sputtering a vanadium target in an O2+Ar ambient followed by annealing at 400°C in N2. We use wide spectral range ellipsometry spanning the infrared to ultraviolet to characterize the complex optical response of VO2 thin films in situ over a range of temperatures crossing the SMT. The parametric optical properties fully describe the modification of spectral features as the temperature changes. Ultimately, these results are used to effectively track switching between semiconducting and metallic states in situ, in real time, as the film is thermally cycled across the SMT. |
Saturday, September 29, 2018 10:00AM - 10:15AM |
E02.00005: Fabrication and Characterization of Copper Indium Telluride Thin Films Kiran Ghimire, Ebin Bastola, Dipendra Adhikari, Prakash Uprety, Randy J. Ellingson, Nikolas Podraza Copper Indium Telluride (CIT) is a semiconducting low band gap (~0.9 eV) material, desirable for bottom cell in tandem solar cell structure in order to extract the more of the solar spectrum. CIT thin films have been fabricated by co-evaporation of Copper, Indium, and Tellurium source materials followed by annealing in Tellurium environment. Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) have been used to find the grain size and stoichiometric proportions. Crystallinity and the phase of the CIT film is determined by using X-ray diffraction (XRD). Spectroscopic Ellipsometry measurements are performed and the complex dielectric function (e = e1 + e2) over the spectral range of interest 0.7 to 2 eV are extracted. The variation in the band gap is also studied in different stochiometric proportionate CIT thin films. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700