• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1204-1207
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• 2009

We investigated the device performance of bulk heterojunction solar cells depending on the active layer thickness. For the systematic comparison, the polymer solar cells comprising RR-P3HT:PCBM (1:0.8 (wt%:wt%)) blend films with different thickness were characterized by impedance spectroscopy, and J-V measurement in dark and solar simulated illumination. The device with 120 nm thickness of active layer exhibited maximum power conversion efficiency of 3.5 % under AM 1.5 100mW/$cm^2$ illumination condition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.589-594
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• 2016

P3HT:PCBM bulk heterojunction solar cells added with ferroelectric polymer were fabricated and characterized. By incorporating P3HT:PCBM solar cell with P(VDF-TrFE) ferroelectric additive, the power conversion efficiency was increased up to nearly 50%. Photoacoustic analysis on this phenomena was carried out for the first time. Through this study, we find that the ferroelectricity of the polymer additive plays the key role in the enhancement of the power conversion efficiency of the organic solar cell by suppressing the non-radiative recombination of charge transfer exciton more effectively.

• Current Photovoltaic Research
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• v.5 no.3
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• pp.69-74
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• 2017

Here we report the influence of thermal treatment on the performance of high efficiency polymer solar cells with the bulk heterojunction films of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b'] dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] (PTB7-Th) and [6,6]-phenyl $C_{71}$ butyric acid methyl ester ($PC_{71}BM$). The crystalline nanostructure of PTB7-Th:$PC_{71}BM$ layers, which were annealed at three different temperatures, was investigated by employing synchrotron radiation grazing incidence X-ray diffraction (GIXD) technique. Results showed that the device performance was slightly reduced by thermal annealing at $50^{\circ}C$ but became significantly poor by thermal annealing at $100^{\circ}C$. The poor device performance by thermal annealing was attributed to the collapse in the crystalline nanostructure of PTB7-Th in the PTB7-Th:$PC_{71}BM$ layers as evidenced by the GIXD measurements that exhibited huge reduction in the intensity of PTB7-Th (100) peak even at $50^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.70-75
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• 2011

We introduced nanoscale interfacial layers between the PV layer and the cathode in poly (3-hexylthiophene):methanofullerene bulk-heterojunction polymer photovoltaic (PV) cells. The nanoscale double interfacial layers were made of ultrathin poly (oxyethylenetridecylether) surfactant and low-work-function alloy-metal of Al:Li layers. It was found that the nanoscale interfacial layers increase the photovoltaic performance, i.e., increasing short-circuit current density and fill factor with improved device stability. For PV cells with the nanoscale double interfacial layers, an increase in power conversion efficiency of $4.18{\pm}0.24%$ was achieved, compared to that of the control devices ($3.89{\pm}0.08%$) without the double interfacial layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.20-20
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• 2010

Organic based photovoltaics (OPV) have been received a lot of attention because they are lightweight, inexpensive to fabricate and flexible compare to crystalline Si solar cells. In this seminar, several important progresses in the Polymer PV, such as, formation of bulk heterojunction, development of post annealing technique, tandem cell fabrication will be introduced. In addition that, some efforts to achieve the further improvement in the performance of the Polymer PV will be discussed.

• Current Photovoltaic Research
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• v.8 no.4
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• pp.107-113
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• 2020

Here we report the long-term stability of polymer:nonfullerene solar cells which were stored under dark and indoor light condition. The polymer:nonfullerene solar cells were fabricated using bulk heterojunction (BHJ) layers of poly[(2,6-(4,8-bis(5-(2-ethylhexyl) thiophen-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). To investigate their long-term stability, the PBDB-T:IT-M solar cells were stored in an argon-filled glove box. One set of the fabricated solar cells was completely covered with an aluminum foil to prevent any effect of light, whereas another set was exposed to indoor light. The solar cells were subjected to a regular performance measurement for 40 weeks. Results revealed that the PBDB-T:IT-M solar cells underwent a gradual decay in performance irrespective of the storage condition. However, the PBDB-T:IT-M solar cells stored under indoor light condition exhibited relatively lower power conversion efficiency (PCE) than those stored under the dark. The inferior stability of the solar cells under indoor light was explained by the noticeably changed optical absorption spectra and dark spot generation, indicative of degradations in the BHJ layers.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.481.2-481.2
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• 2014

Bulk hetero junction (BHJ) polymer solar cell (PSCs) is one of the most promising fields as alternative energy source. Especially, the development of new p-type conjugated polymer is one of the main issues to get core technology. In this study, we investigated the chemical doping effects of incorporating 3,6-carbazole units into conjugated polymers based on 2,7-carbazole. We assessed the structural effects of this chemical doping by measuring the photovoltaic device performance of the copolymers with and without annealing. Note that the use of nanostructures in the bulk heterojunction layer could be a major obstacle to commercialization because nano-morphologies are frequently unstable at high temperatures. Therefore, the development of thermally stable polymer:fullerene blends with optimized PCEs is an important goal in this area of research. We studied the morphologies of the copolymers incorporating 3,6-carbazole units resulting from thermal annealing to investigate the effects of the difference between the T g values of the 2,7-carbazole unit and the 3,6-carbazole unit.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.246-249
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• 2007

현재까지 $P3HT:C_{60}-PCBM$계는 고분자 유기 태양전지에서 가장 좋은 효율을 보여주고 있다. 그러나 보다 고효율의 소자 제작을 위해 신재료에 대한 연구들이 활발히 진행되고 있으며, 본 연구에서는 $C_{60}-PCBM$ 대신 $C_{70}-PCBM$을 합성하여 소자를 제작하였다. $C_{70}-PCBM$은 $C_{60}-PCBM$에 비하여 가시광선 영역에서 상대적으로 높은 광흡수율을 보여 주었으며, 이것은 광전류의 향상을 가져왔다. 소자제작의 주요 변수로 $P3HT:C_{70}-PCBM$ 광활성층의 처리 조건, 즉, 용매, 조성비, 열처리 조건, 광활성층의 두께 등을 조절하였는데, buffer층(LiF 층) 등이 도입되지 않은 간단한 제작조건 하에서도 본 $C_{70}-PCBM$는 $C_{60}-PCBM$계에 버금가는 3.5% (AM 1.5G, 100 $mW/cm^{2}$ 조건) 이상의 효율을 나타내었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.252-256
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• 2013

We introduced sensitizing dyes into the bulk-heterojunction (BHJ) photovoltaic (PV) layer of polymer solar cells (PSCs). The sensitizing dyes doped were Bis(tetra butyl ammonium) cis-dithio cyanato bis(2,2'-bipyridine-4-carboxylicacid-4'-carboxylate) ruthenium (II) (N719 dye) and the BHJ PV layer used was made of poly (3-hexylthiophene) (P3HT) and phenyl $C_{61}$-butyric acid methyl ester (PCBM). It was found that the N719 dyes increase the photovoltaic performance, i.e., increasing open-circuit voltage and short-circuit current density with improved fill factor. For the P3HT:PCBM PV cells doped with the N719 dyes (0.24 wt%), an increase in power conversion efficiency of 4.0% was achieved, compared to that of the control cells (3.6%) without the N719 dyes.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.559-565
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• 2011

The following noble series of statistical copolymers, poly[(2-(3-thienyl)ethanol n-butoxycarbonylmethylurethane)-co-3-hexylthiophene] (PURET-co-P3HT), were synthesized by the chemical dehydrogenation method using anhydrous $FeCl_3$. The structure and electro-optical properties of these copolymers were characterized using $^1H$-NMR, UV-visible spectroscopy, elemental analysis, GPC, DSC, TGA, photoluminescence (PL), and cyclic voltammetry (CV). The statistical copolymers, PURET-co-P3HT (1:0, 2:1, 1:1, 1:2, 1:3), were soluble in common organic solvents and easily spin coated onto indium-tin oxide (ITO) coated glass substrates. Hybrid bulk heterojunction photovoltaic cells with an ITO/G-PEDOT/PURET-co-P3HT:PCBM:Ag nanowires/$TiO_x$/Al configuration were fabricated, and the photovoltaic cells using PURET-co-P3HT (1:2) showed the best photovoltaic performance compared with those using PURET-co-P3HT (1:0, 2:1, 1:1, 1:3). The optimal hybrid bulk heterojunction photovoltaic cell exhibits a power conversion efficiency (PCE) of 1.58% ($V_{oc}$ = 0.82 V, $J_{sc}$ = 5.58, FF = 0.35) with PURET-co-P3HT (1:2) measured by using an AM 1.5 G irradiation (100 mW/$cm^2$) on an Oriel Xenon solar simulator (Oriel 300 W).