Abstract
Temperature-modulated space-charge-limited-current spectroscopy (TMSCLC) is applied to quantitatively evaluate the density of trap states in the band-gap with high energy resolution of semiconducting hybrid lead halide perovskite single crystals. Interestingly multicomponent deep trap states were observed in the pure perovskite crystals, which assumingly caused by the formation of nanodomains due to the presence of the mobile species in the perovskites.
Highlights
Organometallic and inorganic halide perovskites are prospective candidates to replace conventional inorganic materials in the photovoltaic application[1,2,3,4,5,6,7,8] and, in solid states lasers[9], light-emitting diodes[10], photodetectors[11] and solar fuels production[12]
As it can be seen from the experimental current-voltage characteristic (Fig. 1), the current is influenced by the barrier up to 0.3 V, it is ohmic (I~V) in the voltage range (0.3–1.2) V. It is a superlinear dependence (I∼Vm) with non-constant exponent m (m increases with voltage). It suggests the presence of charge carrier traps distributed in energy
For higher voltages the I–V characteristic is typical for the material with Gaussian distribution of traps for charge carriers[33,34]
Summary
As it can be seen from the experimental current-voltage characteristic (Fig. 1), the current is influenced by the barrier up to 0.3 V, it is ohmic (I~V) in the voltage range (0.3–1.2) V It is a superlinear dependence (I∼Vm) with non-constant exponent m (m increases with voltage). It follows from equations below that each point in the SCL current-voltage characteristic comprises the information about the trap density which influences the current value at the given Fermi level EF. In ohmic region (γ = 1) is this position proportional to activation energy Ea0 = EF0 − EV, where EF0 is position of Fermi level in thermodynamic equilibrium For this reason the activation energy of the current (conductance) was measured for each applied voltage in range of (0–3) V, with step 28 mV. That Fermi level position represents the energy at which the localized state (trap) is filled during the measurement of current-voltage characteristic. The dependence of the Fermi level on the initial voltage value (V0 ≈ 0.03 V)
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