Wild band edges: The role of bandgap grading and band-edge fluctuations in high-efficiency chalcogenide devices

• Published in: 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC) pp. 0309 - 0314
• Main Authors: Repins, Ingrid, Mansfield, Lorelle, Kanevce, Ana, Jensen, Soren A., Kuciauskas, Darius, Glynn, Stephen, Barnes, Teresa, Metzger, Wyatt, Burst, James, Chun-Sheng Jiang, Dippo, Patricia, Harvey, Steve, Teeter, Glenn, Perkins, C., Egaas, Brian, Zakutayev, Andriy, Alsmeier, Jan-Hendrik, Lusky, Thomas, Korte, Lars, Wilks, Regan G., Bar, Marcus, Yanfa Yan, Lany, Stephan, Zawadzki, Pawel, Ji-Sang Park, Suhuai Wei
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.06.2016
• Subjects: Annealing; Cadmium compounds; CAS; CdTe; CIGS; CTS; CZTS; defect; Fluctuations; grading; Grain boundaries; II-VI semiconductor materials; Performance evaluation; Photonic band gap
• DOI: 10.1109/PVSC.2016.7749600

Band-edge effects - including grading, electrostatic fluctuations, bandgap fluctuations, and band tails - affect chalcogenide device efficiency. These effects now require more careful consideration as efficiencies increase beyond 20%. Several aspects of the relationships between band-edge phenomena and device performance for NREL absorbers are examined. For Cu(In, Ga)Se 2 devices, recent increases in diffusion length imply changes to the optimum bandgap profile. The origin, impact, and modification of electrostatic and bandgap fluctuations are also discussed. The application of the same principles to devices based on CdTe, kesterites, and emerging absorbers (Cu 2 SnS 3 , CuSbS 2 ), considering differences in materials properties, is examined.