Inorganic–organic interfaces in hybrid solar cells

Abstract

In this review, we present important concepts to describe inorganic-organic interfaces in hybrid solar cells. We discuss the formation of hybrid interfaces, provide an introduction to the ground-state electronic structure of the individual components, and detail the overall electronic landscape after combining into a hybrid material for different relevant cases. We then explore the impact of hybrid interfaces on photophysical processes that are crucial for the photovoltaic performance of hybrid solar cells. Within this framework, we discuss methods for hybrid interface modification toward the optimization of hybrid solar cells, such as doping, the application of interlayers, and morphological control.

Advanced characterization of organic–metal and organic–organic interfaces: from photoelectron spectroscopy data to energy-level diagrams

“…The functionality of virtually all organic and hybrid (opto-)electronic devices depends on interface energetics, and a thorough understanding of energy-level alignment mechanisms at organic-metal and organic-organic interfaces is indispensable for further efficiency improvements [1][2][3][4][5]. For example, the energy-level offset at the donor-acceptor interface in organic photovoltaic devices is crucial for exciton dissociation [6][7][8]; chemisorbed molecular monolayers on metals can tune the substrate work functions by an interfacial charge transfer [9,10] and allow, consequently, to lower charge injection barriers into electrodes [11,12].…”

“…(1) The push-back effect decreases the VL at both interfaces (figures 1(a) and (b)) upon deposition of the contact layer (1 ML) [5,42]. (2) The bond dipole increases the VL due to interfacial charge transfer at the chemisorptive interface (figure 1(a)) [39,43].…”

Hybrid Organic-Inorganic Materials and Interfaces With Mixed Ionic-Electronic Transport Properties: Advances in Experimental and Theoretical Approaches

“…The electronic interactions in h OI materials have been extensively studied particularly for sensing, energy storage and energy conversion applications ( Kumar et al, 2018 ; Singh et al, 2019 ; Duan et al, 2020 ; Niederhausen et al, 2021 ; Rathnayake et al, 2021 ; Zhang et al, 2021 ). The electronic interactions in these h OI materials and interfaces are mostly via proximity of the π -cloud of the organic phase with the inorganic surface, and thus Class I h OI materials are the most studied for these purposes.…”

Energetic disorder impacts energy-level alignment of alpha-sexithiophene on hydrogen-terminated silicon and silicon oxide

“…The energy-level alignment (ELA) at the ubiquitous interfaces of (opto-)electronic applications is decisive for device performance [1][2][3]. Actually, hybrid organic-inorganic interfaces can add functionality to devices, e.g., they can serve as charge-carrier selective contacts for photovoltaic cells [4,5] and thin layers of organic semiconductors (OSCs) can tune ELA at such interfaces [6]. The ELA between inorganic semiconductors like Si and OSCs can be rather complex, e.g., for rodlike organic semiconductors like pentacene or tetracene the orientation of the long molecular axis with respect to the surface ('standing' or 'lying' molecules) is decisive for ELA [7,8].…”

“…The ELA between inorganic semiconductors like Si and OSCs can be rather complex, e.g., for rodlike organic semiconductors like pentacene or tetracene the orientation of the long molecular axis with respect to the surface ('standing' or 'lying' molecules) is decisive for ELA [7,8]. In the absence of chemical interaction, ELA is mainly determined by the substrate work function (WF) and the ionization energy (IE) and electron affinity (EA) of the OSC thin film [3,5]. In addition to these quantities also the width of the density of states (DOS) of the frontier molecular orbitals (highest occupied molecular orbital, HOMO and lowest unoccupied molecular orbital, LUMO) of the OSC thin film plays an important role for ELA, in particular, if Fermi-level pinning is involved [9,10].…”