High‐Efficiency Photovoltaic Conversion at Selective Electron Tunneling Heterointerfaces

Abstract

particular, highly efficient photogenerated electron-hole pair separation, transport, and collection at the heterointerface are the key to achieve high photon-to-current conversion efficiency for photovoltaic devices. [12][13][14][15] Therefore, interface engineering was widely applied to control the photoinduced charge transport processes at the heterointerface for improving the performance of photovoltaic devices. [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. Therefore, such an ISET effect at the heterointerface has great potential to be applied for efficient photovoltaic conversion.Due to a highly photoactive and unique amphiphilic structure, Z907 ruthenium molecules were widely used as the dye sensitizer in all-solid-state dye-sensitized solar cells. [22] In this work, Z907 molecules were chosen as the photoactive material to construct a Z907/SLG/TiO 2 ternary interface. As shown in Figure 1a, the photoexcited electrons in Z907 molecules are expected to tunnel across SLG and ballistically inject into the conductance band (CB) of the TiO 2 semiconductor layer, while photoexcited holes in Z907 molecules can only transport to the SLG semimetal layer. After that, the electron and hole are collected by the TiO 2 layer and the SLG layer, respectively, and further transport to the outside circuit for photoelectric conversion. Based on such an ISET mechanism, the electron transparency of the graphene layer is crucial for the high-efficiency photovoltaic conversion in ISET-based photovoltaic devices. Considering the fact that the electron transparency decreases with increasing the thickness of graphene, [23] single-layer graphene was chosen to construct the ISET-based heterointerface. With such an ISET-based heterointerface, we investigated the photoinduced carrier dynamic processes and photoelectric conversion performances at the heterointerface.Effectively controlling photoinduced charge transport at the heterointerface is of crucial importance for improving the performance of photovoltaic devices. On the basis of an ipsilateral selective electron tunneling (ISET) mechanism, here this study investigates photoinduced charge transport and photovoltaic conversion at a simplified dye/single-layer graphene (SLG)/TiO 2 ternary interface. With an amphiphilic Z907 molecule as the model dye, the photoexcit...

Van der Waals Heterostructures by Design: From 1D and 2D to 3D

“…41 Finally, considering VDW interactions represent a universal force between any two given materials, the VDW-integration approach can be broadly expanded to virtually any material systems as long as the interface is flat enough or at least one component is compliant enough to allow the interface to naturally relax to VDW distance to activate the VDW interaction. In this regard, with proper design, conventional 3D materials can also be integrated into the family of VDW heterostructures to produce 2D/ 3D mixed-dimensional VDW heterostructures or even 3D/3D VDW heterostructures for further enriched electronic 42,43 and optoelectronic 44,45 functions. The VDW heterojunctions could be created by flexible physical assembly of prefabricated building blocks 30,31,33,[46][47][48] or direct VDW epitaxy growth process.…”

Redox Control of Charge Transport in Vertical Ferrocene Molecular Tunnel Junctions

“…Au/SAM/graphene heterostructures, 21,22 where single-layer graphene (SLG) acts as the top electrode and electricity flows in a cross-plane direction, perpendicular to the SAM. Because the SLG exhibits both partial electrical transparency [38][39][40] and selective material permeability, 41 we were motivated to determine if charge transport and chemical and electrochemical reactions could be separated across the graphene layer. Here, we demonstrate this unique capability by constructing a vertical tunnel junction composed of a Fc-SAM, where the separation of chemical or electrochemical redox reactions across the SLG takes place, allowing the in situ control of redox states of Fc groups to tailor the Fc/SLG interfacial coupling strength.…”

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 .…”

“…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.…”