Enhancement of electrical and photo-electrical properties of P3HT:CrCl2 thin films for photo sensing applications

Abstract

In this work, doped and undoped P3HT thin films are prepared and deposited onto ITO interdigitated electrodes. To improve the optical and the electrical properties of the pure P3HT thin film, chromium(II) chloride was used as dopant material with three different weight percentage, 2.5%, 5%, 10%. Room-temperature current–voltage (I-V) characteristics of the samples were measured, showing an increase in the electrical current with increasing the dopant concentration. Under dark condition, the conductivity and resistivity of the pure P3HT thin films were enhanced by a factor of 5× as a result of doping the P3HT by 10 wt% of CrCl2. Under light intensity (50 mW cm−2) and at 10 V bias, the conductivity and resistivity obtained from P3HT:CrCl2 (10 wt%) thin films are 4.75 × 10−4 S cm−1 and ∼2 kΩ, respectively. These results exhibit an enhancement by a factor of ∼12× compared to those obtained from pure P3HT thin film. The current of the photo-sensors based on doped/undoped P3HT thin films are measured as a function of time under light intensity ranging from 0 to 50 mW cm−2 at 1 V bias, exhibiting high photo-response and good reproducibility. Three different wavelengths, white, green, and red were used as light sources to expose the photo-sensors. Under white light, photo-sensor based on P3HT:CrCl2(10 wt%) exhibit the highest values of the photo-responsivity and quantum efficiency, ∼23.3 mA W−1 and 5.8%, respectively, showing an enhancement by a factor of ∼ 11.5× compared to those obtained from the photo-sensor based on pure P3HT.