• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.61.2-61.2
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• 2015

In the past decades, green energy, such as solar energy, wind power, hydropower, biomass energy, geothermal energy, and so on, has been widely investigated and developed to solve energy shortage. Recently, organic solar cells have attracted much attention, because they have many advantages, including low-cost, flexibility, light weight, and easy fabrication [1-3]. Organic solar cells are as a potential candidate of the next generation solar cells. In this abstract, to improve the power conversion efficiency and the stability, the inverted polymer solar cells with various structures were developed [4-6]. The novel cell structures included the P3HT:PCBM inverted polymer solar cells with AZO nanorods array, with pentacene-doped active layer, and with extra P3HT interfacial layer and PCBM interfacial layer. These three difference structures could respectively improve the performance of the P3HT:PCBM inverted polymer solar cells. For the inverted polymer solar cells with AZO nanorods array as the electronic transportation layer, by using the nanorod structure, the improvement of carrier collection and carrier extraction capabilities could be expected due to an increase in contact area between the nanorod array and the active layer. For the inverted polymer solar cells with pentacene-doped active layer, the hole-electron mobility in the active layer could be balanced by doping pentacene contents. The active layer with the balanced hole-electron mobility could reduce the carrier recombination in the active layers to enhance the photocurrent of the resulting inverted polymer solar cells. For the inverted polymer solar cells with extra P3HT and PCBM interfacial layers, the extra PCBM and P3HT interfacial layers could respectively improve the electron transport and hole transport. The extra PCBM interfacial layer served another function was that led more P3HT moving to the top side of the absorption layer, which reduced the non-continuous pathways of P3HT. It indicated that the recombination centers could be further reduced in the absorption layer. The extra P3HT interfacial layer could let the hole be more easily transported to the MoO3 hole transport layer. The high performance of the novel P3HT:PCBM inverted polymer solar cells with various structures were obtained.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.512-515
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• 2016

A new viologen derivative namely 1,1'-bis(3,4-dihydroxybutyl)-[4,4'-bipyridine]-1,1'-diium bromide (V-Pr-2OH) was synthesized and applied as a cathode buffer layer to inverted polymer solar cells (PSCs) based on the blend of PTB7 : $PC_{71}BM$. PSCs with the structure of ITO/V-Pr-2OH/PTB7 : $PC_{71}BM/MoO_3/Ag$ as the cathode buffer layer showed the power conversion efficiency (PCE) up to 7.28%, which is comparable to that of the PSCs with the structure of ITO/ZnO/PTB7 : $PC_{71}BM/MoO_3/Ag$ (7.44%) in the absence of V-Pr-2OH. This study demonstrates that a highly efficient PSCs without any high temperature heat treatment can be obtained.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.569-574
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• 2014

Inverted bulk hetero-junction polymer solar cells (iPSC) composed of P3HT/PC61BM blends on the ZnO modified with benzoic acid derivatives-based self-assembled monolayers (SAM) are fabricated. Compared with the device using the pristine ZnO, the devices with ZnO surface modified SAMs derived from benzoic acid such as 4-(diphenylamino)benzoic acid (DPA-BA) and 4-(9H-carbazol-9-yl)benzoic acid (Cz-BA) as an electron transporting layer show improved the performances. It is mainly attributed to the favorable interface dipole at the interface between ZnO and the active layer, the eective passivation of the ZnO surface traps, decrease of the work function and facilitating transport of electron from PCBM to ITO electrode. The power conversion eciency (PCE) of iPSCs based on DPA-BA and Cz-BA treated ZnO reaches 2.78 and 2.88%, respectively, while the PCE of the device based on untreated ZnO is 2.49%. The open circuit voltage values ($V_{oc}$) of the devices with bare ZnO and SAM treated ZnO are not much different. Whereas, higher the fill factor (FF) and lower the series resistance ($R_s$) are obtained in the devices with SAMs modification.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.400.1-400.1
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• 2016

Interfacial engineering approaches as an efficient strategy for improving the power conversion efficiencies (PCEs) of inverted polymer solar cells (iPSCs) has attracted considerable attention. Recently, polymer surface modifiers, such as poly(ethyleneimine) (PEI) and polyethylenimine ethoxylated (PEIE), were introduced to produce low WF electrodes and were reported to have good electron selectivity for inverted polymer solar cells (iPSCs) without an n-type metal oxide layer. To obtain more efficient solar cells, quantum dots (QDs) are used as effective sensitizers across a broad spectral range from visible to near IR. Additionally, they have the ability to efficiently generate multiple excitons from a single photon via a process called carrier multiplication (CM) or multiple exciton generation (MEG). However, in general, it is very difficult to prepare a bilayer structure with an organic layer and a QD interlayer through a solution process, because most solvents can dissolve and destroy the organic layer and QD interlayer. To present a more effective strategy for surpassing the limitations of traditional methods, we studied and fabricated the highly efficient iPSCs with mono-layered QDs as an effective multi-functional layer, to enhance the quantum yield caused by various effects of QDs monolayer. The mono-layered QDs play the multi-functional role as surface modifier, sub-photosensitizer and electron transport layer. Using this effective approach, we achieve the highest conversion efficiency of ~10.3% resulting from improved interfacial properties and efficient charge transfer, which is verified by various analysis tools.

• Current Photovoltaic Research
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• v.1 no.1
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• pp.59-62
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• 2013

We investigated the effects of ZnO thin film deposition methods on the performance of inverted polymer solar cells with a structure of ITO/ZnO/P3HT:PCBM/MoO3/Al. The ZnO thin films were deposited by various methods (spin coating of nanoparticles, sol-gel process, atomic layer deposition) and their morphology was analyzed by atomic force microscopy (AFM). The device with ZnO nanoparticle thin films showed the highest power conversion efficiency of 3 % with low series resistance and high shunt resistance. The superior performance of the device with the ZnO nanoparticle layer is attributed to better electron extraction capability.

• Current Photovoltaic Research
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• v.7 no.3
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• pp.55-60
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• 2019

Polymer:nonfullerene solar cells with an inverted-type device structure were fabricated by employing the bulk heterojunction (BHJ) active layers, which are composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(6-methyl-2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M). The BHJ layers were formed on a pre-patterned indium-tin oxide (ITO)-coated glass substrate by spin-coating using the blend solutions of PBDB-T and IT-M. The solar cell performances were investigated with respect to the cell position on the ITO-glass substrates. In addition, the short-term shelf lifetime of solar cells was tested by storing the PBDB-T:IT-M solar cells in a glovebox filled with inert gas. The results showed that the performance of solar cells was relatively higher for the cells close to the center of substrates, which was maintained even after storage for 24 h. In particular, the PCE of PBDB-T:IT-M solar cells was marginally decreased after storage for 24 h owing to the slightly reduced fill factor, even though the open circuit voltage was unchanged after 24 h.