Effects of Surface Passivation on Trap States, Band Bending, and Photoinduced Charge Transfer in P3HT/TiO₂ Hybrid Inverse Opals

Abstract

We investigate the effect of a common TiO2 passivation reagent, TiCl4, on the photoinduced charge transfer of poly­(3-hexylthiophene) (P3HT) to TiO2 in the inverse opal structure. Treating the inorganic oxide framework with TiCl4 leads to an increase in the size of the TiO2 nanoparticles, a thickening of the inverse opal framework, and a decrease in the trap-state photoluminescence. These changes lead to different energy alignments at the interface. In comparison to the unpassivated P3HT/TiO2 inverse opal, we measured a larger polaron yield, by as high as ninefold, and significantly shorter and more uniformly distributed polaron lifetimes in TiCl4-treated samples. We show that downward band bending in the polymer can be circumvented by tuning the trap states on the metal oxide using TiCl4, thereby eliminating the energetic barrier for photoelectron injection from the polymer to the metal oxide. The findings suggest a way to overcome a potential factor that has plagued the performance of metal oxide–polymer hybrid photovoltaics.

Photocurrents in crystal‐amorphous hybrid stannous oxide/alumina binary nanofibers

“…In nanomaterials, slow electron diffusion has been related to the localized energy states within the band gap as a result of poor crystallinity . This issue has been addressed by coupling absorption and photoluminescence spectroscopies and evaluated trap states via Urbach energy ( E U ) and Stoke shift.…”

“…53 In nanomaterials, slow electron diffusion has been related to the localized energy states within the band gap as a result of poor crystallinity. 54 This issue has been addressed by coupling absorption and photoluminescence spectroscopies and evaluated trap states via Urbach energy (E U ) and Stoke shift. The energy gap of the samples was calculated from the absorption spectra via Tauc's plot technique, showing narrowing energy gap, from 3.7 to 3.4 eV 7 for SnO 2 and Al 2 O 3 , respectively ( Figure 6).…”

Selective Release of Different Neurotransmitters Emulated by a p–i–n Junction Synaptic Transistor for Environment‐Responsive Action Control

“…Under positive V D and V G , the current is determined by the diffusion mechanism, and most of the carriers can travel through the contact surface to form a current. The current‐rectifying characteristics of the junction are generated, [ 26–29 ] so the current in the third quadrant ( V D < 0 and V G < 0) turns on slowly, and shows a weakening trend after the voltage increases to about 3.8 V. While a positive pulse is applied to the ionic gel, electrons collect in the P3HT/PEO layer to form an inversion layer, which increases carrier‐storage capacity and excellent long‐term plasticity in the TiO 2 thin film. [ 30,31 ] Finally, the two signals are collected and combined in the electrode to output the final signal; i.e., potentiation or inhibition.…”

Inorganic–organic interfaces in hybrid solar cells

“…Another kind of interlayer is the terminating surface layer. For example, TiCl 4 is a common passivation reagent for TiO 2 that can be used for trap-state engineering [399]. For elemental ISCs like Si, the simplest termination consists of hydrogen.…”