Ambipolar Charge Photogeneration and Transfer at GaAs/P3HT Heterointerfaces

Abstract

Recent work on hybrid photovoltaic systems based on conjugated polymers and III-V compound semiconductors with relatively high power conversion efficiency revived fundamental questions regarding the nature of charge separation and transfer at the interface between organic and inorganic semiconductors with different degrees of delocalization. In this work, we studied photoinduced charge generation and interfacial transfer dynamics in a prototypical photovoltaic n-type GaAs (111)B and poly(3-hexyl-thiophene) (P3HT) bilayer system. Ultrafast spectroscopy and density functional theory calculations indicate the coexistence of electron and hole transfer at the GaAs/P3HT interface, leading to the generation of long-lived species and photoinduced absorption upon creation of hybrid interfacial states. This opens up new avenues for the use of low-dimensional III-V compounds (e.g., nanowires or quantum dots) in hybrid organic/inorganic photovoltaics, where advanced bandgap and density of states engineering may also be exploited as design parameters.

Molecular‐Level Switching of Polymer/Nanocrystal Non‐Covalent Interactions and Application in Hybrid Solar Cells

“…Conversely, upon selective excitation of PbS NCs, PIA spectrum of the hybrid composite shows little, if any, P3HT delocalized polaron signal superimposed to PbS NC photo-induced absorption feature (compare black and red spectra in panel a of Figure 6, respectively) implying that hole transfer from PbS NCs to P3HT is hindered. Despite previous reports accounting for NC-to-CP hole transfer, 38,39 a slight contribution of such photo-induced process to the generation of mobile charge carriers in hybrid composites has been argued. 40 In our nanocomposites however, the decay of PbS NC first excitonic peak bleaching is longer in presence of P3HT (Figure 6b), whereas the ground state of P3HT appears as depopulated upon PbS NC selective excitation (Figure 6a and 6c).…”

Perovskite Materials for Light‐Emitting Diodes and Lasers

“…Engineering of high-Q optical cavities and high-quality resonator cavities for loss compensation would also be essential to effect reduction in gain thresholds. Although optically pumped polariton lasing has been observed in ZnO, [141] GaAs, [142] and GaN [143] systems, perovskite polariton lasers remain largely unexplored despite some early work in the mid-2000s. [144,145] The quantum-confined systems offered by lower-dimensionality layered perovskites and nanostructures would be top candidates to be explored for polariton lasing since they would allow for gain build-up to occur at much lower carrier lasing thresholds and allow for potentially thresholdless lasing with highly optimized cavities.…”

Organic Optoelectronic Materials: Mechanisms and Applications

“…Panahandeh-Fard et al combined ultrafast spectroscopy with DFT to show the coexistence of subpicosecond electron and hole transfer at the GaAs/P3HT interface, which generated long-lived (>1 ns) hybrid interfacial states. Ambipolar CT has been observed in organic–organic HJs as well and is a potentially promising concept for optimization of PCE in all-organic or hybrid devices.…”