Optical properties influence of the polarization and the temperature on heterojunction organic solar cell

We investigate the dark current-voltage properties of P3HT: PCBM based solar cell at different temperatures. The experimental data were fitted using two methods: Analytical Lambert Method, and Two Regions Method. Several electrical parameters such as: ideality factor n, series resistance Rs and shunt resistance Rsh were determined. The ideality factor for this device is bigger than unity which is discussed in terms: (i) existence of trap levels due to impurities in the band gap and (ii) the presence of tunneling conduction. It is shown that the J-V curves are driven by different effects depending on voltage and temperature ranges. By fitting the temperature dependence of the equivalent circuit's, we extract many essential parameters such as: potential barrier (phi b), Poole Frenkel coefficient beta p, mobility mu, and carrier concentration. It is shown that at low temperature the transport properties are governed by Schottky effect while at high temperature the Poole-Frenkel effect is prevailing.