Interfacial energy level alignments between low-band-gap polymer PTB7 and indium zinc oxide anode

Shin, Dongguen; Lee, Jeihyun; Park, Soo Hyung; Jeong, Junkyeong; Seo, Ki Won; Kim, Hyo Joong; Kim, Han Ki; Choi, Min Jun; Chung, Kwun Bum; Yi, Yeonjin

doi:10.7567/apex.8.095701

Cited by 19 publications

(9 citation statements)

References 37 publications

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“…The LUMO levels were calculated by considering the measured HOMO levels by UPS and the corresponding charge-transporting gaps (2.50 eV for P3HT, 2.25 eV for PTB7, and 2.20 eV for PCBM). 39,50 As a result, we obtained the E HOMO−D − E LUMO-A of P3HT:PCBM and PTB7:PCBM equal to 1.03 and 1.23 eV, respectively. The origin of the difference of electronic structure between P3HT:PCBM and PTB7:PCBM might be due to the difference in positive energy integer charge transfer state (E ICT+ ) of the two polymers.…”

Section: Resultsmentioning

confidence: 82%

“…According to the XPS and UPS results, the energy level diagrams of P3HT:PCBM and PTB7:PCBM can be obtained as shown in Figure . The LUMO levels were calculated by considering the measured HOMO levels by UPS and the corresponding charge-transporting gaps (2.50 eV for P3HT, 2.25 eV for PTB7, and 2.20 eV for PCBM). , As a result, we obtained the E HOMO–D – E LUMO‑A of P3HT:PCBM and PTB7:PCBM equal to 1.03 and 1.23 eV, respectively. The origin of the difference of electronic structure between P3HT:PCBM and PTB7:PCBM might be due to the difference in positive energy integer charge transfer state ( E ICT+ ) of the two polymers. , The relatively small E ICT+ of P3HT has been reported with strong charge transfer to other materials in contact, which possibly facilitates the large energy level shifting .…”

Section: Resultsmentioning

confidence: 99%

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Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices

Yang

Cheng

et al. 2016

ACS Appl. Mater. Interfaces

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Energy level alignment at the organic donor and acceptor interface is a key to determine the photovoltaic performance in organic solar cells, but direct probing of such energy alignment is still challenging especially for solution-processed bulk heterojunction (BHJ) thin films. Here we report a systematic investigation on probing the energy level alignment with different approaches in five commonly used polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM) BHJ systems. We find that by tuning the weight ratio of polymer to PCBM the electronic features from both polymer and PCBM can be obtained by photoemission spectroscopy. Using this approach, we find that some of the BHJ blends simply follow vacuum level alignment, but others show strong energy level shifting as a result of Fermi level pinning. Independently, by measuring the temperature-dependent open-circuit voltage (VOC), we find that the effective energy gap (Eeff), the energy difference between the highest occupied molecular orbital of the polymer donor (EHOMO-D) and lowest unoccupied molecular orbital of the PCBM acceptor (ELUMO-A), obtained by photoemission spectroscopy in all polymer:PCBM blends has an excellent agreement with the extrapolated VOC at 0 K. Consequently, the photovoltage loss of various organic BHJ photovoltaic devices at room temperature is in a range of 0.3-0.6 V. It is believed that the demonstrated direct measurement approach of the energy level alignment in solution-processed organic BHJ will bring deeper insight into the origin of the VOC and the corresponding photovoltage loss mechanism in organic photovoltaic cells.

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Section: Resultsmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices

Yang

Cheng

et al. 2016

ACS Appl. Mater. Interfaces

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“…Furthermore, band bending was observed upon introducing P0 and P4 interlayers in films of ITO/PEDOT : PSS, [21,24] owing to the formation of interfacial dipoles with P0 and P4. [25][26][27] The work function of P0 and P4 is increased by the removal of hydrocarbons through ozone treatment at the interface with ITO, [25,26] and the sulfur group of P4 forms a higher dipole and induces a relatively larger band bending at P4 than at P0. [27] Therefore, the introduction of P4 can improve charge transport and suppress current injection in perovskite devices.…”

Section: Resultsmentioning

confidence: 99%

Versatile Pendant Polymer for Selective Charge Carrier Transport via Controlling the Supramolecular Self‐Assembly

et al. 2021

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Polyvinyl carbazole (P0)-based pendant polymers were synthesized by modifying carbazole motifs with pyrene derivatives (P1 and P4) to manipulate the bandgap and frontier orbital energy levels. To establish the electronic properties of pendant polymers according to structural differences, the polymers were utilized as additional hole transport layers in planar-type perovskite solar cells and organic photovoltaic cells. When P4 with thiophene-pyrene pendant was used as hole transport layer, all device parameters, except open-circuit voltage, were significantly improved in comparison with P0 and P1 (conjugated with t-butyl pyrene derivatives). Since P4 had more electrically conductive thiophene units than benzene units with fewer alkyl groups, the supramolecular assembly of P4 was found to be more favorable in electronic devices. Furthermore, devices with P4 demonstrated lower dark current than others, which could potentially be useful for charge carrier transport and sensitive photo detecting devices.

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“…The energy level alignments at the interfaces of poly(3-hexylthiophene-2,5-diyl) (P3HT)/CuSCN/indium tin oxide (ITO) were determined and compared with that of P3HT/ITO, which is a typical donor/anode system in OPVs. In situ deposition of a P3HT layer on CuSCN with a stepwise deposition-measurement sequence was conducted using vacuum electrospray deposition (VESD), which enabled incremental deposition of a polymer layer to probe its interfacial electronic structure. − It was revealed that the highest occupied molecular orbital (HOMO) of P3HT is aligned with the band-tail states of CuSCN, and thus, barrier-less hole extraction between P3HT and CuSCN occurs. This hole barrier reduction was also confirmed with current density–voltage ( J – V ) measurements of hole-dominated devices.…”

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confidence: 99%

Band-Tail Transport of CuSCN: Origin of Hole Extraction Enhancement in Organic Photovoltaics

Kim

Park

Jeong

et al. 2016

J. Phys. Chem. Lett.

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Copper thiocyanate (CuSCN) is known as a promising hole transport layer in organic photovoltaics (OPVs) due to its good hole conduction and exciton blocking abilities with high transparency. Despite its successful device applications, the origin of its hole extraction enhancement in OPVs has not yet been understood. Here, we investigated the electronic structure of CuSCN and the energy level alignment at the poly(3-hexylthiophene-2,5-diyl) (P3HT)/CuSCN/ITO interfaces using ultraviolet photoelectron spectroscopy. The band-tail states of CuSCN close to the Fermi level (EF) were observed at 0.25 eV below the EF, leading to good hole transport. The CuSCN interlayer significantly reduces the hole transport barrier between ITO and P3HT due to its high work function and band-tail states. The barrier reduction leads to enhanced current density-voltage characteristics of hole-dominated devices. These results provide the origin of hole-extraction enhancement by CuSCN and insights for further application.

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Interfacial energy level alignments between low-band-gap polymer PTB7 and indium zinc oxide anode

Cited by 19 publications

References 37 publications

Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices

Probing the Energy Level Alignment and the Correlation with Open-Circuit Voltage in Solution-Processed Polymeric Bulk Heterojunction Photovoltaic Devices

Versatile Pendant Polymer for Selective Charge Carrier Transport via Controlling the Supramolecular Self‐Assembly

Band-Tail Transport of CuSCN: Origin of Hole Extraction Enhancement in Organic Photovoltaics

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