Temperature dependence of the optical energy gap and Urbach’s energy of CuIn5Se8

Abstract

The optical properties of the ordered defect compound CuIn5Se8, which crystallizes in a hexagonal structure, have been studied by the absorption technique. The analysis of the data shows that the band gap energy EG varies from 1.23 to 1.13 eV between 10 and 300 K. It is found that the variation of EG with temperature is due to the contribution of both acoustic and optical phonons with a characteristic phonon energy of about 14 meV. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy indicating the presence of Urbach’s tail. The phonon energy hνp associated with Urbach’s tail, which is found to be 53 meV, is higher than the highest optical phonon mode reported for this compound, which is about 29 meV. The origin of the additional energy is attributed to the contribution of localized modes produced by structural disorder of low energy formation. An empirical relation, also used earlier in the case of 1:1:2 and other ordered defect compounds of the 1:3:5 phases, explains very well the variation of Urbach’s energy with temperature.

Spin orbit and tetragonal crystalline field interaction in the valence band of CuInSe2‐related ordered vacancy compound CuIn7Se12

“…However, it is observed that the different additive absorption regions cannot be fitted with a single value each of A c and E g . In the energy range 1.3-1.65 eV, a band gap of E g1 = 1.37 eV obtained by extrapolating the straight-line portion of the (αhν) 2 versus hν graph to the x-axis at y = 0 (Fig. 6) explains the transition and yields the value of A c1 as 9.43 × 10 6 .…”

“…Many reports have been published on studies of the OVCs CuIn 5 Se 8 , CuIn 3 Se 5 , CuIn 2 Se 3.5 , etc. [1][2][3][4][5][6][7], but there are few on the OVC CuIn 7 Se 12 .…”

Optical Absorption and Piezoelectric Effect Investigation in Single Crystal of AgGaGe3Se7.6Te0.4 Solid Solution

“…[20]. Отримані результати сили електрон-фононної взаємодії є типовими для кристалів, що мають дефекти стехіометрії [21,22].…”

Optical and Photoelectric Properties of CuGa5Te8 Single Crystals and In/p-CuGa5Te8 Structures

“…These compounds have also been much investigated because of the necessity of searching for new approaches to the control of fundamental properties of triple chalcogenides [5,6]. The majority of these compounds are crystallized in the tetragonal structure of chalcopyrite and are characterized by an ordered arrangement of stoichiometric vacancies in the crystal lattice; for them, the rule of four electrons per atom is fulfilled.…”