p-type doping effect on the performance of organic-inorganic hybrid solar cells

The doping effects in poly(3-hexylthiophene) (P3HT) on the hybrid n-Si/P3HT solar cells were investigated. Oxygen and tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) doping in P3HT could dramatically improve the device performance. The improvements were related to the Fermi level shift in P3HT towards its highest occupied molecular orbital, leading to a larger built-in voltage generated at the n-Si/P3HT interface for favorable charge transfer. This Fermi level shift was ascribed to the electron transfer from P3HT to the dopant, which was characterized by the absorption spectra and the photoluminescence lifetime. Solution-based F4-TCNQ displayed as a potential candidate to p-doped conjugated polymer to improve charge transfer/transport properties for the hybrid solar cells.