The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Effect of temperature on tunneling and quantum efficiency in cigs solar cells
Author:	Liu, Sizhan
View Online:	njit-etd2014-033 (xii, 82 pages ~ 1.9 MB pdf)
Department:	Committee for the Interdisciplinary Program in Materials Science and Engineering
Degree:	Master of Science
Program:	Materials Science and Engineering
Document Type:	Thesis
Advisory Committee:	Ravindra, N. M. (Committee chair) Opyrchal, Halina (Committee member) Zhou, Tao (Committee member) Ahn, Ken Keunhyuk (Committee member)
Date:	2014-01
Keywords:	Band-to-band tunneling Quantum efficiency
Availability:	Unrestricted
Abstract:	Utilizing the two-band approximation and Wentzel-Kramers-B ri l l oui n (WKB) approximation, by including the temperature-dependent effective masses and nonparabolicity effects, an investigation of the temperature dependent band-to-band tunneling process is discussed. In comparison with the parabolic approximation and non- parabolic approximation, the tunneling probability is strongly dependent on the non-parabolicity factor. The temperature dependence of the energy band gap, electron effective mass and light hole effective mass is investigated. The tunneling current density function is derived by a series representation of the incomplete gamma function with non-parabolic effect and its variation at low temperature is also investigated. When the Fermi level of holes is in excess of that of electrons, i.e., EFp>>EFn, the current density function can be successfully simplified as the Fowler-Nordheim formulation. The quantum efficiency model, for CIGS solar cells, is discussed. Device modeling and simulation studies of a Cu(In1−x,Gax)Se2 (CIGS) thin film solar cell are carried out. A variety of graded band-gap structures, including space charge region (SCR) grading, back surface region grading, and double grading of the CIGS absorber layer are considered. A position-dependent absorption coefficient α(x, hv) is obtained by a differential equation for the photon flux φ(x, hv). The quantum efficiency can be calculated by IQE=(φ1-φ2)/φ3. The temperature dependence of the quantum efficiency is also investigated in this thesis.