(377d) Correlating Interfacial Interactions and Macroscopic Photovoltaic Properties of Self-Assembled Hybrid Materials

Correlating interfacial interactions and macroscopic photovoltaic
properties of self-assembled hybrid materials

Justin
P. Jahnke¹, Shany Neyshtadt², Tamar Segal-Peretz², Maria Diaz-Garcia³,
Gitti L. Frey², Brad F. Chmelka^1*

¹ Department of Chemical Engineering, University of California, Santa Barbara

²  Department of Materials Engineering, Technion
- Israel Institute of Technology

³ Department of Applied Physics, University of Alicante, Spain

The use of surfactant-directed mesostructured inorganic materials allows for the preparation of oxide frameworks as
continuous transparent films with high inorganic-organic interfacial contact
and the inclusion of diverse functional guest species. For example, mesostructured titania films (with ca. 10 nm
channel dimensions) containing light-absorbing conjugated guest species exhibit
photovoltaic properties that are influenced strongly by solution processing
conditions. Solution compositions must be chosen for compatibility with the dissimilar
molecular components, which co-assemble into functional hybrid materials as the
solvent is removed. Subsequent integration of these materials into photovoltaic
devices leads to performances that depend on many factors, including the
degree of exciton dissociation at the conjugated guest-titania interface and
charge transport to the electrodes.  The degree of exciton dissociation is
strongly influenced by the extent of interfacial contact between the conjugated
guest species and titania network, while charge transport may be enhanced by
the introduction of orientational order. Detailed molecular-level understanding
of the interactions, mobilities, and proximities among the different functional
components in the hybrid materials can be obtained through solid-state two-dimensional
NMR and other techniques and correlated with macroscopic photo-current
properties.  In particular, judicious selections of the synthesis and
processing conditions are demonstrated to promote enhanced interfacial contact
and charge carrier transport, leading to improved photovoltaic device
performance.  Resulting insights allow mesostructured titania-conjugated
polymer hybrid materials and device properties to be controllably
modified and optimized.