Abstract
After a general introduction into the Shockley theory of current voltage (J–V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite–titanate p–n heterojunctions made of n-doped SrTi1−yNbyO3, y = 0.002 and p-doped Pr1−xCaxMnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J–V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron–polaron hole–polaron pair generation and separation at the interface.
Highlights
At present, photovoltaic devices are mainly based on high purity elemental or compound inorganic semiconducting materials with large electronic bandwidths
An electron beam-induced current (EBIC) scan across the p–n interface is shown in Figure 3b, together with a simulated EBIC linescan, taking into account only the generation volume and the space charge region
We assume that the determined barrier height, EB = 283.5 meV, in the reverse direction is strongly decreased due to the buildup of a large electric field at the junction interface. In this contribution we have analyzed the current–voltage characteristics of a PCMO–STNO junction in the framework of the one diode model based on Shockley theory
Summary
Photovoltaic devices are mainly based on high purity elemental or compound inorganic semiconducting materials with large electronic bandwidths. The doping of such semiconductors allows for the variation in the electrical conductivity and character of the charge carriers. In this way, junctions based on p- or n-doped materials can be tailored. Junctions based on p- or n-doped materials can be tailored In these materials, the charge carriers are quasi-free, that is, the effective mass is relatively small, the mobility is large and the diffusion length of excited electron–hole pairs can be in the 100 μm range for indirect semiconductors [1].
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