Impact of Al3+ incorporation on microstructural pattern, optical and electrical behaviors of PbS:Al3+ films from an alkaline chemical bath

Abstract

The great improvement in electrical conduction of PbS films is still critical for the application of PbS-infrared detectors and solar cells so far. The incorporation of certain ions to PbS is proved effective for the improvement in electrical conduction. Herein a series of face-centered cubic Al3+-incorporated PbS (PbS:Al3+) films with improved electrical conduction are synthesized on p-type Si(100) substrates from an alkaline chemical bath. The impact of Al3+ molar concentration (CAl) is intensively studied on the microstructural pattern, optical and electrical behaviors of the films. The mechanism of the formation of highly crystallized PbS:Al3+ in alkaline chemical bath is also proposed. All the PbS:Al3+ films are slightly rich in Pb. The strong coordination between Pb2+ and organic triethanolamine molecules plays a key role in the formation of highly crystallized PbS:Al3+. The incorporated Al3+ weakens and even destroys the preferred 〈200〉 orientation of the films due to the enhanced crystal lattice distortion. The film’s resistivity is firstly reduced and then increased with increase in CAl, and the near-infrared optical absorption edge slightly blueshifts and then redshifts. The change in resistivity with increase in CAl can be explained by the substitution of Pb2+ by Al3+ and the change in crystallite size, and the slight blue and red shift in optical edge with increase of CAl is mainly attributed to the increase and the decrease in tensile stress of the films caused by the Al3+ incorporation into PbS, respectively.