Electrical and Photoelectric Properties of Organic-Inorganic Heterojunctions PEDOT:PSS/n-CdTe

Abstract

PEDOT: PSS thin films are widely used as transparent coatings in flexible semiconductor devices including solar cells. However, they are not widely used as transparent coatings in combination with crystal substrates. This work shows the possibility of using PEDOT:PSS thin films as a frontal transparent conducting layer in hybrid organic-inorganic Schottky type heterojunctions of the PEDOT:PSS/n‑CdTe, which were prepared by deposition of PEDOT:PSS thin films (using the spin-coating method) on crystalline cadmium telluride substrates. The current-voltage (in a wide temperature range) and capacitance-voltage (at room temperature) characteristics of heterojunctions were measurement and analyzed. It has been established that PEDOT:PSS/n-CdTe heterojunctions have good diode properties with a high rectification ratio RR≈10⁵, a potential barrier height φ₀ = 0.95 eV, and series R_s = 91 Ohm and shunt R_sh = 5.7 × 10⁷ Ohm resistances. Analysis of the forward branches of the I–V characteristics of heterojunctions showed that the dominant charge transfer mechanisms are determined by the processes of radiative recombination at low biases (3kT/e <V <0.3 V) and tunneling through a thin depleted layer at high biases (0.3 V <V <0.6 V). Capacity-voltage characteristics are plotted in the Mott-Schottky coordinate, taking into account the influence of series resistance, measured at a frequency of 1 MHz. Used the C-V characteristic was determined the value of the built-in potential V_c = 1.32 V (it correlates well with the cutoff voltage determined from the current-voltage characteristics) and the concentration of uncompensated donors in the n-CdTe substrate N_D-N_A = 8.79 × 10¹⁴ cm^-3. Although the photoelectric parameters of unoptimized PEDOT:PSS/n-CdTe heterojunctions are low, their photodiode characteristics (Detectivity D^*> 10¹³ Jones) are very promising for further detailed analysis and improvement. The proposed concept of a hybrid organic-inorganic heterojunction also has potential for use in inexpensive γ- and X-ray detectors.