Electrical conductivity and the effect of temperature on photoconduction of n-ZnSe/p-Si rectifying heterojunction cells

Abstract

Electrical and photoelectrical measurements are made at different temperatures on heterojunction photovoltaic cells fabricated by vacuum deposition of n-ZnSe thin films onto p-Si single crystals. A complete study of the current as a function of voltage and temperature is carried out in order to gain fundamental information on trap depth, trap distribution and position of the Fermi level. The results are consistent with space-charge-limited conduction due to an exponentially decreasing distribution of traps. At low voltages, the dark current in the forward direction varies exponentially with voltage. Under reverse bias, the conduction process is interpreted in terms of a transition from electrode-limited Schottky emission to the bulk-limited Poole-Frenkel effect. The values of thermal activation energy for photoconduction and effective density of conducting states are determined and found to be 0.22 eV and 4.4 × 10 17 cm −3 , respectively. These values are estimated from the dependence of photocurrent on temperature at constant illumination with an input power density of 50 mW cm −2 .

Investigation of temperature-dependent electrical properties of p-VOPc/n-si heterojunction under dark conditions

“…To remove surface oxide, chemical etching of n-Si was done with HF/NH 4 F/H 2 O (2:7:1) composition for 90 s [3]. After etching, the silicon wafer was washed for 2 min in pure alcohol and distilled water in an ultrasonic bath and dried in N 2 gas.…”

“…The performance of organic semiconductors is highly influenced by temperature [3][4][5]. Parameters like reverse saturation current, I o , ideality factor, n, series resistance, R s , and shunt resistance, R sh , control the effect of temperature on the performance of heterojunction devices like organic diodes, organic field effect transistors and, particularly, solar cells which are generally exposed to temperatures varying from 10 to 50°C.…”

“…Darwish et al [3] studied the current density-voltage (J-V) characteristics of n-ZnSe/p-Si heterojunction cell at varying temperatures from 295 to 388 K under dark as well as under a constant illumination (50 mW/cm 2 ). Short circuit current density, J sc , and efficiency, η, of the cell were found to increase with increasing temperature.…”

Frequency Dependent Dielectric Properties of ZnSe/p-Si Diode

“…With the current interest in the optoelectronic applications of heterojunctions, II-VI compounds have been employed with Si based heterojunction as a promising materials for photodetector and also photovoltaic diodes [1][2][3][4]. This type of diode structure associates the advantageous properties of the highly transparent, direct-band gap ZnSe window layer and the high mobility, tractable properties of Si layer [5].…”

Growth of ZnSe films on ZnO–Si templates

“…as electroluminescent cells [1], photoelectric cells- [2] and visible sensitive emitter bipolar transistors [3] have all been demonstrated. Although we can indeed grow ZnSe-based epitaxial layers on Si substrates, large mismatches of lattice constant and thermal expansion coefficient between ZnSe and Si will always result in a defective epitaxial layer [4].…”