PEIE capped ZnO as cathode buffer layer with enhanced charge transfer ability for high efficiency polymer solar cells

Li, Ping; Cai, Lun; Wang, Gang; Zhou, Da Chen; Xiang, Jin; Zhang, Yu Jun; Bao, Ding; Alameh, Kamal; Song, Qunliang

doi:10.1016/j.synthmet.2015.02.021

Cited by 35 publications

(19 citation statements)

References 48 publications

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“…In order to overcome this rapid interface degradation of the PHJ‐PSCs devices and to enhance its performance, we introduced the PEIE as interface modification layer. The PEIE can form surface dipole and thus decrease the work function of the cathode, which is widely confirmed by many previous works . The modified work function of electrode will minimize electrical losses upon injection or extraction of electrons.…”

Section: Resultssupporting

confidence: 56%

Improved efficiency and short‐term stability of the planar heterojunction perovskite solar cells with a polyelectrolyte layer

Xiong

Zhan

et al. 2017

Physica Status Solidi (a)

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The power conversion efficiency and the short-term stability of the perovskite solar cells (PSCs) are very important for their commercialization. The decay of the planar heterojunction PSCs (PHJ-PSCs) based on p-i-n structure (ITO/ PEDOT:PSS/CH 3 NH 3 PbI 3 /PCBM/Al) dramatically took place when they were exposed in air. We confirmed that the electrode bubble was responsible for this quick degradation and revealed a preliminary physical mechanism as well. A polyelectrolyte layer (ethoxylated polyethylenimine, PEIE) was inserted into the interface between the active layer and the cathode to enhance the interface contact and facilitate the charge carrier extraction. The power conversion efficiency (PCE), open circuit voltage (V oc ), and fill factor (FF) were found to be enhanced with the PEIE insertion. In addition, the PEIE layer largely improved the interface stability. The PEIE insertion could prohibit the formation of the electrode bubbles, which dramatically enhance the short-term air stability of the devices. The T 50 (time for performance to decay to 50% of its initial measured value) of the devices with PEIE layer was 90 min, which was enhanced by 9 times compared with that without any modification layer. These results provide important information for understanding the decay of the PHJ-PSCs, which may benefit the application of PSCs.

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Section: Resultssupporting

confidence: 56%

Improved efficiency and short‐term stability of the planar heterojunction perovskite solar cells with a polyelectrolyte layer

Xiong

Zhan

et al. 2017

Physica Status Solidi (a)

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“…Conjugated poly‐electrolytes, such as PEIE or PEI, are commonly used as ETLs to decrease the WF of transparent conductive or metal electrodes and to lower the interfacial energy barrier for the electron transport from the active layer to the electrode by forming a thin interfacial dipole between the active layer and the ETL. The power conversion efficiency of the devices can be improved using a conjugated polymer electrolyte or metal oxides as ETLs in an inverted structure . However, the use of ZnO nanoparticles (NPs) can lead to electron trapping and a high series resistance because of the presence of traps/defects with adsorbed oxygen at the NP surfaces .…”

Section: Resultsmentioning

confidence: 99%

“…In our previous works, we demonstrated the preparation of a spray‐coated active layer using low‐bandgap polymers such as poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b’]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7) and 2,6‐bis(trimethyltin)‐4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b’]dithiophene (PBDTTT‐C‐T) along with xylene, which is a nonchlorinated solvent with low amounts of volatile organic compounds compared to chlorinated solvents. It has been demonstrated that a polyethylenimine ethoxylated (PEIE)‐based electron transporting layer (ETL) can be prepared by replacing the more toxic 2‐methoxyethanol with eco‐friendly solvents, such as water or ethanol, to allow the use of another electron selective layer such as zinc oxide (ZnO) . There has been no progress in the production of a full spray polymeric device; indeed, in the work of Zhang et al, only two layers (PAL and hole transporting layer [HTL]) are reported in the direct structure.…”

Section: Introductionmentioning

confidence: 99%

Indium Tin Oxide–Based Fully Spray‐Coated Inverted Solar Cells with Nontoxic Solvents: The Role of Buffer Layer Interface on Low‐Bandgap Photoactive Layer Performance

et al. 2019

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In bulk heterojunction solar cells, the morphology of the interfaces between the photoactive layer (PAL) and charge transporting layers during the deposition process plays a key role in achieving high‐efficiency devices. Herein, an inverted fully spray‐coated solar cell fabricated on an indium tin oxide (ITO)‐glass substrate is presented. It is demonstrated that a spray‐coated double electron transporting layer composed of zinc oxide (ZnO) nanoparticles coated with polyethylenimine ethoxylated (PEIE) improves the morphology of the spray‐coated active layer on top of the spray‐coated cathode. Moreover, focusing on the hole transporting layer and anode, the performance obtained using a commercial poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) blend is compared with a high‐conductive anhydrous PEDOT:PSS (A‐PEDOT) mixed with a commercial PEDOT:PSS (CPP‐105D) as transporting layer. By optimizing the spray deposition of all the layers, a fully scalable spray process is used to produce polymer solar cells with ITO/ZnO/PEIE/poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b’]dithiophene‐2,6‐diyl] [3‐fluoro‐2‐ [(2‐ethylhexyl)carbonyl] thieno[3,4‐b]thiophenediyl]] (PTB7): [6,6]‐phenyl‐C70‐butyric‐acid‐methyl‐ester (PC70BM)/CPP:A‐PEDOT structure, achieving a power conversion efficiency (PCE) of 3.6%. Such result is significant if compared to a spray‐coated structure with evaporated anode (MoO3‐Ag). In this case (ITO/ZnO/PEIE/PTB7:PCBM/MoO3‐Ag), a power conversion efficiency of 5.5% is obtained.

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“…15 New fullerene 16 and nonfullerene acceptors 17 with higher-lying lowest unoccupied molecular orbitals (LUMOs) require electron contacts with a low work function. 18 Multijunction tandem devices 19 and inverted structure solar cells 20 introduce further complexity in matching energy levels of the active layers and the electrodes.…”

Section: ■ Introductionmentioning

confidence: 99%

“…For example, the work function of indium tin oxide (ITO) was lowered by almost 1 eV, which was attributed to the molecular dipoles of the ethylamine dipole as well as an interfacial dipole formed by physisorption of PEIE on the contact surface. 20,34,38 Distinguishing the various effects of interfacial layers is often challenging experimentally. One of the key questions addressed in this work is to what extent interfacial layers increase the V oc of the devices because of better work function alignment between the active materials and the contacts, as opposed to increased V oc because of reduced recombination.…”

Section: ■ Introductionmentioning

confidence: 99%

Effects of Interfacial Layers on the Open Circuit Voltage of Polymer/Fullerene Bulk Heterojunction Devices Studied by Charge Extraction Techniques

Saekung

Wright

Clarke

et al. 2019

ACS Appl. Mater. Interfaces

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Interfacial layers are frequently used in organic solar cells performing various functions, including blocking surface recombination, improving selectivity of charge carrier extraction, modification of the work function of the contact materials and enhancing light absorption within the photoactive layer through an optical cavity effect. The aim of this work is to investigate the origin of performance enhancement of bulk heterojunction solar cells using various electron and hole interfacial layers with a particular focus on the improvement to the open circuit voltage (Voc). Solar cells using poly[N-9′-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′benzothiadiazole)](PCDTBT) :)]:[6,6]-phenyl C70-butyric acid methyl ester (PC[70]BM) (1:4) active layers were prepared with a combination of polymeric, metal oxide and polyelectrolyte electron and or hole interfacial layers. Four device structures with i) no interfacial layers (reference); ii) only hole; iii) only electron; iv) both electron and hole interfacial layers were fabricated and compared using current-voltage, transient photovoltage and charge extraction measurements. The voltage gains (ΔVoc) at matched charge density due to work function modification (ΔVoc h or ΔVoc e) is distinguished from the increase in Voc due to increased charge carrier density due to longer charge carrier lifetime. At the hole contact, ΔVoc h was 0.21 V by using a PEDOT-PSS hole interfacial layer, while ΔVoc e was 0.29 V on the electron contact using a PEI-TiOx interfacial layer compared to reference devices. The electron lifetime also improved by orders of magnitude with the use of either electron or hole contact layers, contributing to a further 0.35-0.38 V increase in the open circuit voltage ((ΔVoc rec) due to increased charge density. The increased charge carrier lifetime is proposed to originate from the larger spatial separation of the electrons and holes in the device due to the increased internal field. Using both an electron and a hole interfacial layer didn't significantly increase the charge carrier lifetime compared to single interfacial layer devices, therefore the Voc didn't increase significantly. The findings presented clarify the role of interfacial layers in organic solar cells, and provides new insights into using time resolved charge extraction techniques to understand the influence of interfacial layers on the open circuit voltage.

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PEIE capped ZnO as cathode buffer layer with enhanced charge transfer ability for high efficiency polymer solar cells

Cited by 35 publications

References 48 publications

Improved efficiency and short‐term stability of the planar heterojunction perovskite solar cells with a polyelectrolyte layer

Improved efficiency and short‐term stability of the planar heterojunction perovskite solar cells with a polyelectrolyte layer

Indium Tin Oxide–Based Fully Spray‐Coated Inverted Solar Cells with Nontoxic Solvents: The Role of Buffer Layer Interface on Low‐Bandgap Photoactive Layer Performance

Effects of Interfacial Layers on the Open Circuit Voltage of Polymer/Fullerene Bulk Heterojunction Devices Studied by Charge Extraction Techniques

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