Tin Incorporation in AgInSe2 Thin Films: Influence on Conductivity

Bipolarity with enhanced conductivity has been achieved by tin incorporation in AgInSe2 thin films. Structural and optical characterizations of these films prepared by reactive evaporation indicate that the incorporation neither distorts the tetragonal chalcopyrite structure nor affects the optical band gap of the parent compound. A detailed analysis of the low temperature conductivity of AgInSe2 (AIS) and tin incorporated AgInSe2 (AIS:Sn) suggests domination by variable range hopping, grain boundary effect, and thermal activation of carriers in different temperature regimes. The enhanced conductivity in AIS:Sn is attributed to donor and acceptor defect level formation, which has pushed the Fermi levels to similar to 9 meV below the conduction band edge in n-type films and similar to 3 meV above the valence band edge in p-type films. These improved characteristics of the films are likely to promote their suitability for photovoltaic and thermoelectric power generation applications