Interface Modification Layer Research Articles

Influence of organic interface modification layer on the photoelectric properties of ZnO-based hybrid solar cells

The organic-inorganic heterojunction interface of hybrid solar cells plays an important role on the cell performance. The properties of heterojunction interface were modulated by employing two small organic molecules. The results showed that the introduction of organic molecules could improve the compatibility between the organic and inorganic materials, accelerate excitons separation efficiency and suppress carriers recombination. The power conversion efficiency of device was improved from 0.23% to 1.41%. Furthermore, the charge lifetime and interface charge transfer/recombination mechanisms were analyzed in detail. The intrinsic factors affecting the cell performance were investigated by electrochemical impedance and open circuit voltage decay measurements.

Controllable Spatial Configuration on Cathode Interface for Enhanced Photovoltaic Performance and Device Stability.

The molecular structure of cathode interface modification materials can affect the surface morphology of the active layer and key electron transfer processes occurring at the interface of polymer solar cells in inverted structures mostly due to the change of molecular configuration. To investigate the effects of spatial configuration of the cathode interfacial modification layer on polymer solar cells device performances, we introduced two novel organic ionic salts (linear NS2 and three-dimensional (3D) NS4) combined with the ZnO film to fabricate highly efficient inverted solar cells. Both organic ionic salts successfully decreased the surface traps of the ZnO film and made its work function more compatible. Especially NS4 in three-dimensional configuration increased the electron mobility and extraction efficiency of the interfacial film, leading to a significant improvement of device performance. Power conversion efficiency (PCE) of 10.09% based on NS4 was achieved. Moreover, 3D interfacial modification could retain about 92% of its initial PCE over 160 days. It is proposed that 3D interfacial modification retards the element penetration-induced degradation without impeding the electron transfer from the active layer to the ZnO film, which significantly improves device stability. This indicates that inserting three-dimensional organic ionic salt is an efficient strategy to enhance device performance.

(Invited) Photovoltaic Performance and Stability of Fullerene/Cerium Oxide Double Electron Transport Layer Superior to Single One in P-I-N Perovskite Solar Cells

Interface engineering that involves in the metal cathodes and the electron transport layers (ETLs) facilitates the simultaneous improvement of device performances and stability in perovskite solar cells (PSCs). Herein, low-temperature solution-processed cerium oxide (CeOx) films are prepared by a facile sol-gel method and employed as the interface layers between [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and an Ag back contact to form PC61BM/CeOx double ETLs. The introduction of CeOx enables electron extraction to the Ag electrode and protects the underlying perovskite layer and thus improves the device performance and stability of the p-i-n PSCs. The p-i-n PSCs with double PC61BM/CeOx ETLs demonstrate a maximum power conversion efficiency (PCE) of 17.35%, which is superior to those of the devices with either PC61BM or CeOx single ETLs. Moreover, PC61BM/CeOx devices exhibit excellent stability in light soaking, which is mainly due to the chemically stable CeOx interlayer. The results indicate that CeOx is a promising interface modification layer for stable high-efficiency PSCs.

Photovoltaic performance and stability of fullerene/cerium oxide double electron transport layer superior to single one in p-i-n perovskite solar cells

Interface engineering that involves in the metal cathodes and the electron transport layers (ETLs) facilitates the simultaneous improvement of device performances and stability in perovskite solar cells (PSCs). Herein, low-temperature solution-processed cerium oxide (CeOx) films are prepared by a facile sol-gel method and employed as the interface layers between [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and an Ag back contact to form PC61BM/CeOx double ETLs. The introduction of CeOx enables electron extraction to the Ag electrode and protects the underlying perovskite layer and thus improves the device performance and stability of the p-i-n PSCs. The p-i-n PSCs with double PC61BM/CeOx ETLs demonstrate a maximum power conversion efficiency (PCE) of 17.35%, which is superior to those of the devices with either PC61BM or CeOx single ETLs. Moreover, PC61BM/CeOx devices exhibit excellent stability in light soaking, which is mainly due to the chemically stable CeOx interlayer. The results indicate that CeOx is a promising interface modification layer for stable high-efficiency PSCs.

Induced nano-scale self-formed metal-oxide interlayer in amorphous silicon tin oxide thin film transistors

Amorphous Silicon-Tin-Oxide thin film transistors (a-STO TFTs) with Mo source/drain electrodes were fabricated. The introduction of a ~8 nm MoOx interlayer between Mo electrodes and a-STO improved the electron injection in a-STO TFT. Mo adjacent to the a-STO semiconductor mainly gets oxygen atoms from the oxygen-rich surface of a-STO film to form MoOx interlayer. The self-formed MoOx interlayer acting as an efficient interface modification layer could conduce to the stepwise internal transport barrier formation while blocking Mo atoms diffuse into a-STO layer, which would contribute to the formation of ohmic contact between Mo and a-STO film. It can effectively improve device performance, reduce cost and save energy for the realization of large-area display with high resolution in future.

Interfacial engineering of printable bottom back metal electrodes for full-solution processed flexible organic solar cells * * Project supported by the Research Grant Council of Hong Kong (No. PolyUC5015-15G), the Hong Kong Polytechnic University (No. G-SB06), and the National Natural Science Foundation of China (Nos. 21125316, 21434009, 51573026).

Printing of metal bottom back electrodes of flexible organic solar cells (FOSCs) at low temperature is of great significance to realize the full-solution fabrication technology. However, this has been difficult to achieve because often the interfacial properties of those printed electrodes, including conductivity, roughness, work function, optical and mechanical flexibility, cannot meet the device requirement at the same time. In this work, we fabricate printed Ag and Cu bottom back cathodes by a low-temperature solution technique named polymer-assisted metal deposition (PAMD) on flexible PET substrates. Branched polyethylenimine (PEI) and ZnO thin films are used as the interface modification layers (IMLs) of these cathodes. Detailed experimental studies on the electrical, mechanical, and morphological properties, and simulation study on the optical properties of these IMLs are carried out to understand and optimize the interface of printed cathodes. We demonstrate that the highest power conversion efficiency over 3.0% can be achieved from a full-solution processed OFSC with the device structure being PAMD-Ag/PEI/P3HT:PC61BM/PH1000. This device also acquires remarkable stability upon repeating bending tests.

Efficient and ultraviolet durable planar perovskite solar cells via a ferrocenecarboxylic acid modified nickel oxide hole transport layer.

Planar perovskite solar cells (PSCs) that use nickel oxide (NiOx) as a hole transport layer have recently attracted tremendous attention because of their excellent photovoltaic efficiencies and simple fabrication. However, the electrical conductivity of NiOx and the interface contact properties of the NiOx/perovskite layer are always limited for the NiOx layer fabricated at a relatively low annealing temperature. Ferrocenedicarboxylic acid (FDA) was firstly introduced to modify a p-type NiOx hole transport layer in PSCs, which obviously improves the crystallization of the perovskite layer and hole transport and collection abilities and reduces carrier recombination. PSCs with a FDA modified NiOx layer reached a PCE of 18.20%, which is much higher than the PCE (15.13%) of reference PSCs. Furthermore, PSCs with a FDA interfacial modification layer show better UV durability and a hysteresis-free effect and still maintain the original PCE value of 49.8%after being exposed to UV for 24 h. The enhanced performance of the PSCs is attributed to better crystallization of the perovskite layer, the passivation effect of FDA, superior interface contact at the NiOx/perovskite layers and enhancement of the electrical conductivity of the FDA modified NiOx layer. In addition, PSCs with FDA inserted at the interface of the perovskite/PCBM layers can also improve the PCE to 16.62%, indicating that FDA have dual functions to modify p-type and n-type carrier transporting layers.

溶液法制备PVP为界面修饰层的红荧烯结晶性薄膜

溶液法制备PVP为界面修饰层的红荧烯结晶性薄膜

Fullerene‐Based Materials for Photovoltaic Applications: Toward Efficient, Hysteresis‐Free, and Stable Perovskite Solar Cells

AbstractPerovskite solar cells are promising candidates for next‐generation photovoltaics. Fullerenes and their derivatives can act as efficient electron transport layers, interfacial modification layers, and trap state passivators in perovskite solar cells, all of which play an important role in increasing efficiency, reducing current hysteresis, and enhancing device stability. Herein, recent progress in the use of fullerenes and their derivatives in perovskite solar cells is reviewed, with a particular emphasis on fullerene chemical structures that affect device performance. Potential fullerene candidates that could further improve device performance and stability are also discussed.

N-type small molecule as an interfacial modification layer for efficient inverted polymer solar cells

Interfacial modification layer facilitates the preferable contact property between electron transport layer (ETL) and active layer, which is capable of enhancing the performance of inverted polymer solar cells (PSCs). In this study, we use an n-type organic small molecule of N,N-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) as the interfacial modification layer on the top of ZnO ETL by thermal evaporation. We demonstrate that the PTCDI-C8 layer can reduce the work function of ZnO, so that the efficiency of electron transfer is improved, and the recombination of charge carrier on the contact interface is suppressed. As a consequence, the power conversion efficiency (PCE) increases from 8.26% to 9.29%, based on the poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b]dithiophene-co-3-fluorothieno[3,4-b]-thiophene-2-carboxylate] (PTB7-Th): [6,6]-phenyl-C71-butyricacid methyl ester (PC71BM) bulk heterojunction (BHJ) active layer. The enhanced device performance is attributed to the improvement of short-circuit current (JSC), open-circuit voltage (VOC) and fill factor (FF). This work provides an effective approach to reach high performance inverted PSCs.

A Facile Two-Step Interface Engineering Strategy To Boost the Efficiency of Inverted Ternary-Blend Polymer Solar Cells over 10%

A facile two-step strategy was proposed to modify the ZnO nanoparticles electron transfer layer in inverted ternary blend polymer solar cells (TPSCs) by irradiating the ZnO with UV-ozone (UVO) and then spin-coating the poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl-fluorene)] (PFN) interfacial modification layer. The combination of UVO and PFN showed the advantage of simultaneously passivating the defect states of ZnO to reduce the defect-assisted electron-hole recombination, modifying the surface morphology and hydrophilicity of ZnO to improve the interfacial contact with the active layer, and optimizing the electron transfer characteristic of ZnO to enhance the electron extraction from the active layer to cathode. As a result, the champion power conversion efficiency (PCE) of TPSCs with PTB7-Th:PCDTBT:PC70BM as the active layer was increased from 6.80% to 9.61% by 20 min UVO irradiating, and then further increased to 10.87% after the incorporation of an ultrathin PFN inte...

Poly(sodium 4-styrenseulfonate)-modified monolayer graphene for anode applications of organic photovoltaic cells

An insulated poly(sodium 4-styrenseulfonate) (PSS) was used to modify monolayer graphene for anode applications of organic photovoltaics (OPVs). With this PSS interfacial modification layer, the OPVs showed a significant increase of 56.4% in efficiency due to an improved work function and hydrophilic feature of graphene and an enlarged recombination resistance of carriers/excitons. Doping a highly contorted 1,2,5-thiadiazole-fused 12-ring polyaromatic hydrocarbon into the active layer to form ternary blended OPVs further enlarged the recombination resistance of carriers/excitons and improved light absorption of the active layer, with which a high power conversion efficiency of 6.29% was acquired.

C-H Direct Arylated 6H-Indolo[2,3-b]quinoxaline Derivative as a Thickness-Dependent Hole-Injection Layer.

A novel perfluoro-1,4-phenylenyl 6H-indolo[2,3-b]quinoxaline derivative (TFBIQ) was designed and synthesized by using a C-H direct arylation method. The optoelectrical properties of the obtained TFBIQ were fully characterized by UV/Vis spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, and a group of Alq3 -based green organic light-emitting diodes (OLEDs). Device A, which used 0.5 nm-thick TFBIQ as the interfacial modification layer, exhibited the five best advantages of device performance including a minimum turn-on voltage as low as 3.1 V, a maximum luminescence intensity as high as 26564 cd m-2 , a highest current density value of 348.9 mA cm-2 at a voltage of 11 V, the smallest efficiency roll-off, as well as the greatest power efficiency of 1.46 lm W-1 relative to all of the other tested devices with thicker TFBIQ and also 10 nm-thick MoO3 as hole-injection layers (HILs). As a promising candidate for an organic HIL material, the as-prepared TFBIQ exhibited a strong thickness effect on the performance of corresponding OLEDs. Furthermore, the theoretical calculated vertical ionization potential of the fluorinated TFBIQ suggests better anti-oxidation stability than that of the non-fluorinated structure.

Self-powered narrowband p-NiO/n-ZnO nanowire ultraviolet photodetector with interface modification of Al2O3

All inorganic, self-powered, narrowband, and rapid response p-NiO/n-ZnO nanowire (NW) ultraviolet (UV) photodetectors were fabricated and investigated with Al2O3 as an interface modification layer. Al2O3 films grown by atomic layer deposition can greatly suppress the surface defects on ZnO NWs and improve the p-NiO/n-ZnO NW interface. The photo-response of the photodetector in the 430–500 nm wavelength range was greatly inhibited and the full-width at half-maximum of the response spectrum was less than 30 nm. A large responsivity of 1.4 mA/W was achieved under a 380 nm UV irradiation (0.36 mW/cm2) at zero bias and the response time of the device was less than 0.04 s. Such a simple interface modification method might promote the developing of ZnO NW based narrowband photodetectors.

Efficient quantum dot light-emitting diodes with a Zn0.85Mg0.15O interfacial modification layer.

Efficient inverted quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated by using 15% Mg doped ZnO (Zn0.85Mg0.15O) as an interfacial modification layer. By doping Mg into ZnO, the conduction band level, the density of oxygen vacancies and the conductivity of the ZnO can be tuned. To suppress excess electron injection, a 13 nm Zn0.85Mg0.15O interlayer with a relatively higher conduction band edge and lower conductivity is inserted between the ZnO electron transport layer and QD light-emitting layer, which improves the balance of charge injection and blocks the non-radiative pathway. Moreover, according to the electrical and optical studies of devices and materials, quenching sites at the ZnO surface are effectively reduced by Mg-doping. Therefore exciton quenching induced by ZnO nanoparticles is largely suppressed by capping ZnO with Zn0.85Mg0.15O. Consequently, the red QLEDs with a Zn0.85Mg0.15O interfacial modification layer exhibit superior performance with a maximum current efficiency of 18.69 cd A-1 and a peak external quantum efficiency of 13.57%, which are about 1.72- and 1.74-fold higher than 10.88 cd A-1 and 7.81% of the devices without Zn0.85Mg0.15O. Similar improvements are also achieved in green QLEDs. Our results indicate that Zn0.85Mg0.15O can serve as an effective interfacial modification layer for suppressing exciton quenching and improving the charge balance of the devices.

Interfacial modification layers based on carbon dots for efficient inverted polymer solar cells exceeding 10% power conversion efficiency

Herein, we have demonstrated that rationally-designed carbon dots (C-dots) with amino groups, for the first time, were used as an efficient interfacial modification layer on the ZnO or AZO interlayers, greatly improving the device performance. The C-dots modifying showed decreased work function and smoothed surface of metal oxides, facilitating the enhancement of charge extraction efficiency and the decrease of recombination losses for the cathode. More importantly, the C-dots showed the luminescent down-shifting effect, beneficial for the increase of the light conversion for near ultraviolet and blue-violet portions of sunlight. As a result, by incorporating ZnO/C-dots as the interlayers, our designed inverted polymer solar cells with PTB7:PC71BM as the active layer obtained over 20% enhancement compared with the devices with pure ZnO (from 7.41% to 9.01%). Notably, a maximum PCE of up to 10.24% was achieved with the AZO/C-dots as the interlayers and PTB7-Th:PC71BM instead of PTB7:PC71BM as the active layer, and this efficiency outperforms all previously reported PSCs using carbon materials as additives in the active layer or the interface materials. Our PCE value is also higher than those of many previously reported bulk-heterojunction (BHJ) solar cells using the organic polymer modifier.

Inverted polymer solar cells with enhanced fill factor by inserting the potassium stearate interfacial modification layer

A thin potassium stearate (KSt) film combined with an optimized ZnO film was introduced to improve the fill factor (FF) of highly efficient inverted polymer solar cells (PSCs). Atomic force microscopy and contact angle measurements were used to show that the introduction of KSt did not change the morphology of interlayer. On the contrary, it is beneficial for the spread of the active layer on the interlayer. The origin of enhanced FF was systematically studied by the ideal current-voltage model for a single heterojunction solar cell and electrochemical impedance spectroscopy. On the basis of the data analysis, the reduced charge recombination loss was responsible for this improved FF. At last, when KSt was replaced by sodium stearate (NaSt), the similar experiment phenomenon was observed. This indicates that inserting a metallic stearate modified layer is a promising strategy to enhance inverted PSCs performance.

Low‐Temperature‐Processed 9% Colloidal Quantum Dot Photovoltaic Devices through Interfacial Management of p–n Heterojunction

Low‐temperature solution‐processed high‐efficiency colloidal quantum dot (CQD) photovoltaic devices are developed by improving the interfacial properties of p–n heterojunctions. A unique conjugated polyelectrolyte, WPF‐6‐oxy‐F, is used as an interface modification layer for ZnO/PbS‐CQD heterojunctions. With the insertion of this interlayer, the device performance is dramatically improved. The origins of this improvement are determined and it is found that the multifunctionality of the WPF‐6‐oxy‐F interlayer offers the following essential benefits for the improved CQD/ZnO junctions: (i) the dipole induced by the ionic substituents enhances the quasi‐Fermi level separation at the heterojunction through favorable energy band‐bending, (ii) the ethylene oxide groups containing side chains can effectively passivate the interfacial defect sites of the heterojunction, and (iii) these effects occur without deterioration in the intrinsic depletion region or the series resistance of the device. All of the figures‐of‐merit of the devices are improved as a result of the enhanced built‐in potential (electric field) and the reduced interfacial charge recombination at the heterojunction. The benefits due to the WPF‐6‐oxy‐F interlayer are generally applicable to various types of PbS/ZnO heterojunctions. Finally, CQD photovoltaic devices with a power conversion efficiency of 9% are achievable, even by a solution process at room temperature in an air atmosphere. The work suggests a useful strategy to improve the interfacial properties of p–n heterojunctions by using polymeric interlayers.

Achieving high efficiency and improved stability in large-area ITO-free perovskite solar cells with thiol-functionalized self-assembled monolayers

A promising approach towards highly efficient and stable large-area ITO-free perovskite solar cells is demonstrated by employing thiol-functionalized self-assembled monolayers as interfacial modification layers.

溶胶凝胶法制备以Al2O3为界面修饰层的铪铟锌氧薄膜晶体管

Solution processed Hf In Zn O( HIZO) thin film transistors( TFTs) with Hf Si Oxdielectrics modified by Al_2O_3 layer were fabricated. After the Al2O3 layer was inserted,the optical transmittance of Hf Si Oxfilms was hardly changed and the surface root mean square( RMS) roughness was decreased from 0. 24 to 0. 16 nm. The excellent surface was benefited to improve the interface properties between dielectrics and semiconductors of HIZO TFTs. Furthermore,the characteristics of thin film transistors were improved. The threshold voltage shift between forward and reverse sweep was decreased obviously. Simultaneously, the threshold voltage and subthreshold voltage were decreased,and the on to off current ratios and mobility were increased. Above all,the experiment results indicate that Al_2O_3 film is fit for using in TFTs as the interface modification layer to improve TFTs performance.