Effect of temperature on tunneling and quantum efficiency in cigs solar cells

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., E_{Fp}>>E_{Fn}, 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(In_{1-x},Gax)Se_2 (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 [alpha](x, hv) is obtained by a differential equation for the photon flux [phi](x, hv). The quantum efficiency can be calculated by IQE=([phi]_1-[phi]_2)/[phi]_3. The temperature dependence of the quantum efficiency is also investigated in this thesis.

Name thesis:degree_name

Master of Science in Materials Science and Engineering - (M.S.)

Discipline thesis:degree_discipline

Committee for the Interdisciplinary Program in Materials Science and Engineering

Year

2014

Author dc:creator

• Liu, Sizhan

Contributors dc:contributor

• N. M. Ravindra
• Halina Opyrchal
• Tao Zhou

• Band-to-band tunneling
• Quantum efficiency
• Materials Science and Engineering

Repository record dc:identifier

https://digitalcommons.njit.edu/theses/187

OAI identifier oai:identifier

oai:digitalcommons.njit.edu:theses-1186