Electrical transport mechanisms and photovoltaic characteristics of Au/neutral red/p-Si/Al heterojunction solar cell

Abstract

Uniform thin films of neutral red, NR, have been successfully prepared by thermal evaporation technique. X-ray diffraction patterns showed that the structure of NR film consists of nanocrystallites dispersed in amorphous matrix. Increasing annealing temperature influences crystallite size and quantity of amorphous phase. The high absorption of NR films in visible region of spectra supports the application of NR film as an absorber in photovoltaic devices. Hybrid organic–inorganic heterojunction solar cell, Au/NR/p-Si/Al, was fabricated. The current–voltage characteristics of the heterojunction diode have been studied in the temperature range of 300–355K and in the voltage range (−2 to 2V). The device showed a series resistance of 2.64kΩ, shunt resistance of 237kΩ, rectification ratio of 106 at ±1V and ideality factor of 1.8 at room temperature. It was found that the conduction mechanisms of the diode are controlled by the thermionic emission at forward voltage bias ≤0.2V and space charge limited current (SCLC) conduction in the voltage range 0.2<V≤2V. The capacitance–voltage characteristics of the NR/p-Si device were studied at room temperature in dark condition. Energy band diagram for NR/p-Si device was constructed. The device under illumination with light of intensity 20mW/cm2 gives values of photovoltaic parameters as: open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and power conversion efficiency (η) are 0.46V, 1.78mA, 0.29 and 2.37%, respectively.