Electronic Conduction Mechanisms and Defects in Polycrystalline Antimony Selenide

Abstract

A study of the electronic conduction mechanisms and electrically active defects in polycrystalline Sb 2 Se 3 is presented. It is shown that for temperatures above 200 K, the electrical transport is dominated by thermal emission of free holes, ionized from shallow acceptors, over the intergrain potential barriers. In this temperature range, the temperature dependence of the mobility of holes, limited by the intergrain potential barriers, is the main contributor to the observed thermal activation energy of the conductivity of 485 meV. However, at lower temperatures, nearest-neighbor and Mott variable range hopping transport in the bulk of the grains turn into the dominant conduction mechanisms. Important parameters of the electronic structure of the Sb 2 Se 3 thin film such as the average intergrain potential barrier height ϕ = 391 meV, the intergrain trap density N t = 3.4 × 10 11 cm −2 , the shallow acceptor ionization energy E A0 = 124 meV, the acceptor density N A = 1 × 10 17 cm −3 , the net donor density N D = 8.3 × 10 16 cm −3 , and the compensation ratio k = 0, 79 were determined from the analysis of these measurements.

p‐Type Antimony Selenide via Lead Doping

“…In this case, the conductivity is dominated by thermal emission of free holes over the intergrain potential barriers. [ 37 ] In the middle‐temperature region (170–210 K), the corresponded value of E a2 is 0.084 eV, which relates to a shallow intrinsic defect level. In the low‐temperature region (80–160 K), the conductivity changed very slowly as the temperature decrease.…”

“…Between 230 and 360 K, the linearly fitted activation energy E a1 is around 0.456 eV, which also corresponds to the thermal emission of free holes over intergrain potential barriers. [ 37 ] In the middle‐temperature region (150–220 K), an activation energy E a2 of 0.221 eV is extrapolated. E a2 is related to the shallow acceptor defect of Pb Sb as calculated.…”

Deciphering the Role of Defects in the Ambipolar Electrical Transport in Nanocrystalline Sb2Se3 Thin Films

“…From the application point of view, another interesting result is the mobility of the free carriers not being limited by GPB (φ = 0 meV), contrary to what has been reported for polycrystalline thin films. [ 20 ] These last two results constitute advantages for the design of nanostructured Sb 2 Se 3 ‐based solar cells. Small GPB improve electronic transport and collection efficiency of the cells.…”

“…A similar model considering one acceptor and compensation has been successfully used to fit the temperature dependence of the electrical resistivity in CZTS and p-type Sb 2 Se 3 polycrystalline thin films. [20] For a single donor, with compensation, the temperature dependence of the free electron density and of the electrical conductivity can be calculated as [31] n T N N N N…”

“…The selenization process enhances the grain size in the polycrystalline films [ 17 ] and creates a large concentration of Se Sb acceptors that assures p‐type conductivity. [ 17,20 ] However, Sb 2 Se 3 single crystals and polycrystalline thin films can be grown with n‐type character and are successfully used to produce solar cells with up to 7.7% of conversion efficiency. [ 21 ] We have previously demonstrated the room‐temperature growth and tuning of the optical properties of nanocrystalline Sb 2 Se 3 thin films.…”