Synthesis, electrical transport mechanisms and photovoltaic characteristics of p-ZnIn2Se4/n-CdTe thin film heterojunction

Abstract

The synthesis and electrical transport features of vacuum-deposited p-ZnIn2Se4/n-CdTe (p-ZIS/n-CT) heterojunction diode (HJD) are discussed. Transmission electron microscopy (TEM) was used to characterize the microstructures of p-ZIS and n-CT thin films. The Hall measurement system determined the conductivity and carrier concentration of the ZIS and CT films; the acceptor concentration (Na) for ZIS film and donor concentration (Nd) for CT film observed are 4.12×1013cm−3 and 2.80×1014cm−3, respectively. The DC electrical resistance (R) variation with temperature (T) determines thermal activation (impurity-based conduction) and bandgap energies of p-ZIS and n-CT thin films. Scanning electron microscopy (SEM) was used to look at the surface morphology of p-ZIS/n-CT HJD. The semiconductor characterization system (SCS-4200) was used to characterize the current–voltage (I−V) and capacitance–voltage (C–V) of the p-ZIS/n-CT HJD at different T (303−340K). The p-ZIS/n-CT HJD’s dark I−V finding shows conventional diode nature with a decent rectification ratio (RR) (≃4.34×105at±2.0V). At a given bias, the RR value drops as T increases. The systematic assessment of I−V data suggests the thermionic emission (TE) mechanism at lower bias and the space charge-limited conduction (SCLC) mechanism at higher bias. The quantitative analysis estimates the barrier height (φb) as ≃0.79eV (from I−V measurements) and ≃0.88eV (from C–V measurements). Cheung’s function was utilized to derive the φb, ideality factor (n) and the series resistance (Rs) of the p-ZIS/n-CT HJD. With a rise in T, HJD’s saturation current (Is), n and φb rise, whilst, Rs falls. To gain insight into depletion behaviour, a study examined space charge and electric field distributions for abrupt p-ZIS/n-CT HJD. The experimental findings of Anderson’s model corroborate a theoretical energy band diagram for the p-ZIS/n-CT HJD. The p-ZIS/n-CT HJD’s photovoltaic (PV) characterization resulted in a 0.51 fill factor and 1.04% efficiency. The implications are discussed.