Electrical conduction mechanisms in the temperature-dependent current-voltage characteristics of poly(3-hexylthiophene)/n-type Si devices

The electrical conduction mechanisms in the temperature-dependent current-voltage characteristics of poly(3-hexylthiophene) (P3HT)/n-type Si devices were investigated. Carrier transport in the low forward-voltage region at room temperature is dominated by thermionic emission (TE). However, at high voltages the current is limited by series resistance and space charge limited current (SCLC) mechanisms. It is shown that the ideality factor increases as temperature decreases, because of a TE-to-SCLC transition. In order to obtain a greater understanding of the transition from TE to SCLC behavior, few-layer black phosphorus (BP) was incorporated into P3HT (i.e., P3HT:BP) and the P3HT:BP/n-type Si device was fabricated. It is suggested that the rectifying behavior is affected by the bulk effects of the P3HT layer. However, the incorporation of BP into P3HT leads to a significant increase in the hole mobility, suppressing the bulk effects of the P3HT layer.