Tetrazole as a New Anchoring Group for the Functionalization of TiO₂ Nanoparticles: A Joint Experimental and Theoretical Study

Functional hybrid materials are an important tool for generating original architectures featuring desirable properties for multiple applications. The success in creating innovative materials with valuable functionalities relies on the close interaction between the organic and inorganic parts of the hybrid system. Herein, we report the use of tetrazole as an anchoring group for the photosensitization of TiO₂ nanoparticles by an organic chromophore and the related performance in dye-sensitized solar cells. The interaction mode between the tetrazole motif and TiO₂ was thoroughly investigated by various techniques. The overall study reveals that the optoelectronic and photovoltaic properties of the dye featuring tetrazole rival those of an analogue bearing a carboxylic acid function, even leading to significantly enhanced photovoltage in the device. These results demonstrate the effectiveness of the tetrazole functional group as a serious alternative anchoring group for organic photosensitizers in hybrid materials for energy

Tuning the Interfacial Electronic Structure at Organic Heterojunctions by Chemical Design

Quantum-chemical techniques are applied to assess the electronic structure at donor/acceptor heterojunctions of interest for organic solar cells. We show that electrostatic effects at the interface of model 1D stacks profoundly modify the energy landscape explored by charge carriers in the photoconversion process and that these can be tuned by chemical design. When fullerene C₆₀ molecules are used as acceptors and unsubstituted oligothiophenes or pentacene are used as donors, the uncompensated quadrupolar electric field at the interface provides the driving force for splitting of the charge-transfer states into free charges. This quadrupolar field can be either enhanced by switching from a C₆₀ to a perylene-tetracarboxylic-dianhydride (PTCDA) acceptor or suppressed by grafting electron-withdrawing groups on the donor

Charge Dissociation at Interfaces between Discotic Liquid Crystals: The Surprising Role of Column Mismatch

The semiconducting and self-assembling properties of columnar discotic liquid crystals have stimulated intense research toward their application in organic solar cells, although with a rather disappointing outcome to date in terms of efficiencies. These failures call for a rational strategy to choose those molecular design features (e.g., lattice parameter, length and nature of peripheral chains) that could optimize solar cell performance. With this purpose, in this work we address for the first time the construction of a realistic planar heterojunction between a columnar donor and acceptor as well as a quantitative measurement of charge separation and recombination rates using state of the art computational techniques. In particular, choosing as a case study the interface between a perylene donor and a benzoperylene diimide acceptor, we attempt to answer the largely overlooked question of whether having well-matching donor and acceptor columns at the interface is really beneficial for optimal charge separation. Surprisingly, it turns out that achieving a system with contiguous columns is detrimental to the solar cell efficiency and that engineering the mismatch is the key to optimal performance