High-Efficiency Selective Electron Tunnelling in a Heterostructure Photovoltaic Diode

Abstract

A heterostructure photovoltaic diode featuring an all-solid-state TiO2/graphene/dye ternary interface with high-efficiency photogenerated charge separation/transport is described here. Light absorption is accomplished by dye molecules deposited on the outside surface of graphene as photoreceptors to produce photoexcited electron-hole pairs. Unlike conventional photovoltaic conversion, in this heterostructure both photoexcited electrons and holes tunnel along the same direction into graphene, but only electrons display efficient ballistic transport toward the TiO2 transport layer, thus leading to effective photon-to-electricity conversion. On the basis of this ipsilateral selective electron tunnelling (ISET) mechanism, a model monolayer photovoltaic device (PVD) possessing a TiO2/graphene/acridine orange ternary interface showed ∼86.8% interfacial separation/collection efficiency, which guaranteed an ultrahigh absorbed photon-to-current efficiency (APCE, ∼80%). Such an ISET-based PVD may become a fundamental device architecture for photovoltaic solar cells, photoelectric detectors, and other novel optoelectronic applications with obvious advantages, such as high efficiency, easy fabrication, scalability, and universal availability of cost-effective materials.

Precise Control of Interfacial Charge Transport for Building Functional Optoelectronic Devices

“…To solve the first problem, we and some other groups modified the graphene/environment interface with stimuli‐active components to fabricate graphene‐based hybrid chemical sensors or photodetectors with highly sensitive responses to external stimuli. A variety of graphene composites, such as graphene/polymer composites, have also been used as active sensing materials to improve the performances of graphene‐based gas sensors .…”

“…To promote the development of this field and enable the development of high‐efficiency low‐cost photovoltaic and optoelectronic device architectures, ingenious and reliable interface designs for highly efficient separation and transmission of photogenerated carriers are required . In this regard, our group has developed a unique heterostructure photovoltaic diode with an all‐solid‐state ternary interface (TiO 2 /SLG/dye), which is composed of a TiO 2 electron‐collecting layer, SLG hole‐transporting layer, and monolayer of dye molecules ( Figure a) . Different from the conventional photovoltaic conversion process, in our photovoltaic device, both the electrons and holes generated by photoexcitation can tunnel into the graphene along the same direction, but only the electrons show a highly efficient ballistic transport to the TiO 2 transport layer (Figure b).…”

“…Recently, we and some other groups found that more efficient functional and hybrid devices can be realized by building more complicated ternary interfaces (Figure e) such as semiconductor/recognition receptor/environment interfaces for specific light/chemistry/biosensing (Figure e, left), or a dye/single layer graphene (SLG)/titanium oxide (TiO 2 ) ternary interface, for efficient charge transport and photovoltaic conversion (Figure e, middle and right). The key to this idea is to separate the signal recognition from charge transport, each performing its own functions without interfering with the other.…”

High‐Efficiency Photovoltaic Conversion at Selective Electron Tunneling Heterointerfaces

“…[20,42] With photoexcitation by a 532 nm pulse laser, the transient photovoltage spectrum of the Z907/SLG/TiO 2 photovoltaic device was monitored by an oscilloscope. [43] As shown in Figure 3b …”

“…[16][17][18][19] Recently, we discovered an ipsilateral selective electron tunneling (ISET) mechanism, which can be used to effectively separate photoinduced electron-hole pair at the heterointerface. [20,21] Specifically, when photoactive materials are assembled on the outside surface of single-layer graphene (SLG)/TiO 2 , Schottky diode, photoexcited electrons, as well as holes produced from the photoactive materials transport along the same direction to SLG, whereas only electron can further inject into the TiO 2 layer, thus realizing photogenerated electron-hole pair separation at the Schottky interface. With acridine orange (AO) dye as a model photoactive material, ≈86.8% photocarriers separation/collection efficiency was realized at the AO/SLG/ TiO 2 interface.…”