Energy level tuning at the interface of inorganic and organic semiconductors

Semiconductor heterojunctions are key enablers for advanced electronic and optoelectronic devices, and as a result, researchers have been working to optimize their functionality.

Norbert Koch, of Humboldt University, investigated the combination of inorganic and organic materials in a heterojunction and how to optimize the energy level alignment at the interface of these two materials. By combining two materials with superior but complementary properties, such as charge carrier mobility and light-matter coupling, he found the hybrid structure could perform better overall compared to previous heterojunctions.

“From the different methods that allow energy level tuning, the most interesting is based on inserting an interlayer between two semiconductors,” said Koch.

The interlayer is only one molecular monolayer thick, or about 1 nanometer, and thus it minimally perturbs the two individual materials while enabling wide energy level tuning.

Tailoring intramolecular polar bond distribution and controlling molecular orientation at interfaces also show promise as methods for energy level tuning. With such state-of-the-art methods, the frontier energy levels at an inorganic/organic heterojunction can be varied by up to 3 eV, which covers the energy gap of most semiconductors.

These approaches for energy level tuning can be employed in numerous electronic and optoelectronic devices that require semiconductor heterojunctions, such as light-emitting devices, solar cells, and advanced transistor architectures.

In future research, Koch said it could be interesting to explore further possibilities of multifunctional devices or devices that can be controlled by multiple stimuli, including light, voltage, temperature, and magnetic fields.

Source: “Opportunities for energy level tuning at inorganic/organic semiconductor interfaces,” by Norbert Koch, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0074963 .