Laser Pulses Applications in Photovoltaic Effect

Abstract

Laser pulses have been utilized in detecting photovoltaic properties and exploring functional characteristics in the field of solid-state physics (Jain & Landis, 1998; Sun et al., 2004; Lu et al., 2005; Yan et al., 2007; Jin et al., 2009; Lv et al., 2009). Experimental and theoretical investigations into photovoltaic effect under laser pulse are of particular interest for both physics and engineering. Recent advances in seeking fast photovoltaic response material (Lu et al., 2005; Zhao et al., 2005; Zhao et al., 2006a; Zhao et al., 2006b; Zhao et al., 2006c; Huang et al., 2006), finding one-order-of-magnitude enhancement of lateral photovoltaic (LPV) effect in the perovskite oxide heterostructures compared with the substrates (Jin et al., 2007; Jin et al., 2009), and investigating the dependence of the photovoltaic effect on the thin films and substrates thickness (Qiu et al., 2007; Wen et al., 2009), are attributed to laser pulses applications in the photovoltaic effect. Several years ago, transient photoelectric effects were observed in La0.7Sr0.3MnO3 (LSMO3)/Si heterostructure fabricated by pulsed laser deposition (Lu et al., 2005), which offers opportunities for designing new fast photodetectors. Moreover, the unusual LPV, ascribed to the Dember effect (Pankove, 1971) induced by large numbers of photo-generated carriers under laser pulses, was observed in the heterostructures of both La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 (LSMO1/SNTO) and LSMO3/Si (Jin et al., 2007; Jin et al., 2009). A one-order-of-magnitude enhancement of the LPV was found (Jin et al., 2009). Furthermore, the dependence of photovoltage on the thin films and substrates thickness was presented. The photovoltage becomes larger with the increase of the LSMO1 film thickness, while the film thickness is less than the depletion layer of the heterostructures. This is ascribed to the increase of the carrier amount of the LSMO1 layer and the enhancement of the built-in electric field in the space-charge region of the LSMO1/SNTO heterostructure (Qiu et al., 2007). Faster photoelectric response was observed in LaAlO3-δ/Si (LAO/Si) heterostructures, and the photoelectric sensitivity was greatly improved by decreasing the thickness of the Si substrates (Wen et al., 2009). In order to reveal the underlying physical origin and the dynamic process of the photoelectric effect in the oxide heterostructure, time-dependent drift-diffusion model was employed (Liao et al., 2009a, 2009b, 2009c; Liao et al., 2010; Ge et al., 2010). The theoretical calculations showed that the modulation of Sr doping in LaxSr1-xMnO3 is an effective