Opportunities for energy level tuning at inorganic/organic semiconductor interfaces

Norbert Koch

doi:10.1063/5.0074963

Abstract

The aim of this Perspective is to provide an overview of approaches that can be employed to tune the energy level alignment at interfaces between inorganic and organic semiconductors for use in electronic and optoelectronic devices. The approaches include tailoring intramolecular dipolar bond distribution, controlling molecular orientation at interfaces, and the insertion of a molecularly thin interlayer that abruptly shifts the electrostatic potential between the two semiconductors and, thus, affords level tuning. With these state of the art methods, the frontier energy levels at an inorganic/organic heterojunction can be varied up to ca. 3 eV, i.e., covering the energy gap of most semiconductors. By combining two or more of these approaches or by employing interfacial molecular switches, it is envisioned that unconventional and dynamically switchable interfacial energy level scenarios can be created, enabling expanded or superior device functionality.

Highlights

Semiconductor heterojunctions are key enablers for advanced electronic and optoelectronic devices
Huge efforts have been and still are dedicated to achieve control over the energy levels at interfaces.[2,3]. This is challenging because the formation of covalent bonds at the interface between two dissimilar materials can result in adverse gap states, and crystal lattice mismatch can induce strain and hamper appropriate structure formation
Materials, such as transition metal dichalcogenides, have significant potential in this respect.[4]. Their electronic properties strongly depend on the number of layers, as well as on strain that may be introduced during layer transfer, and energy level tuning for a given material pair has not yet been explored

Summary

INTRODUCTION

Semiconductor heterojunctions are key enablers for advanced electronic and optoelectronic devices. Materials, such as transition metal dichalcogenides, have significant potential in this respect.[4] their electronic properties strongly depend on the number of layers, as well as on strain that may be introduced during layer transfer, and energy level tuning for a given material pair has not yet been explored Instead, this Perspective focuses on organic materials as alternative van der Waals semiconductors for combination with inorganic ones, as several energy level tuning approaches have emerged that hold potential for wider use in devices. Most organic semiconductors—molecules or polymer-based—feature strong light–matter coupling, making them attractive for optoelectronic applications.[5] it is difficult to obtain highest charge carrier mobilities in organic semiconductors Their combination with established inorganic semiconductors, which can exhibit record-high carrier mobility, provides the potential for the combination of the best of the two worlds in inorganic–organic heterojunctions. Different approaches to tune the energy level alignment at their heterojunctions are explained, alongside a few specific examples, and ending with an outlook on how the field could further evolve

RECALLING BASIC ELECTRONIC PROPERTIES OF ISC–OSC INTERFACES

ENERGY LEVEL TUNING VIA MATERIAL DESIGN

ULTRATHIN MOLECULAR INTERLAYERS BETWEEN ISC AND OSC

Findings

OUTLOOK