• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.310-310
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• 2010

Electronic and photovoltaic characteristics of two sensitizers (TA-BTD-CA and TA-BTD-St-CA), composed of a different $\pi$-conjugation in the linker group, have been investigated by theoretical and experimental methods. The electronic structure, transition dipole moment and oscillator strengths of two sensitizers have been scrutinized by using density functional theory (DFT) and time-dependent DFT (TD-DFT) method. The LUMO level and the oscillator strength of TA-BTD-St-CA was higher than that of TA-BTD-CA, which may facilitate the electron injection process as well as increase the absorption coefficient. The relative efficiencies of the electron injection from the excited sensitizer to nanocrystalline TiO2 and SnO2 films have also been investigated by nanosecond transient absorption spectroscopy. The relative electron injection efficiency of TA-BTD-St-CA exhibited similar injection efficiency for two different semiconductors. However, in the case of TA-BTD-CA sensitizer, electron injection into SnO2 was approximately three times larger than that into TiO2. This enhancement of electron injection of TA-BTD-CA for the SnO2 is due to the increment of the driving force caused by positive shift of conduction band of semiconductor, which was also confirmed from the investigation for the photovoltaic characteristics according to the electrolyte additive, such as LiI additive.

• Current Photovoltaic Research
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• v.12 no.1
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• pp.1-5
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• 2024

Perovskite solar cells have exhibited a remarkable increase in efficiency from an initial 3.8% to 26.1%, marking a significant advancement. However, challenges persist in the commercialization of perovskite solar cells due to their low stability with respect to humidity, light exposure, and temperature. Moreover, the instability of the organic charge transport layer underscores the need for exploring inorganic alternatives. In the manufacturing process of the perovskite solar cells' oxide charge transport layer, ultraviolet-ozone (UVO) treatment is commonly applied to enhance the wettability of the perovskite solution. The UVO treatment on metal oxides has proven effective in suppressing surface oxygen vacancies and removing surface organic contaminants. This study focused on the characterization of nickel oxide as the hole transport material in perovskite solar cells, specifically investigating the impact of UVO treatment on film properties. Through this analysis, changes induced by the UVO treatment were observed, and consequent alterations in the device characteristics were identified.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.89.1-89.1
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• 2010

Since Gratzel and co-workers developed a new type of solar cell based on the nanocrystalline $TiO_2$ electrode, dye-sensitized solar cells (DSSCs) have attracted considerable attention on account of their high solar energy-to-conversion efficiencies (11%), their easy manufacturing process with low cost production compared to conventional p-n junction solar cells. The mechanism of DSSC is based on the injection of electrons from the photoexcited dye into the conduction band of nanocrystalline $TiO_2$. The oxidized dye is reduced by the hole injection process from either the hole counter or electrolyte. Thus, the electronic structures, such as HOMO, LUMO, and HOMO-LUMO gap, of dye molecule in DSSC are deeply related to the electron transfer by photoexcitation and redox potential. To date, high performance and good stability of DSSC based on Ru-dyes as a photosensitizer had been widely addressed in the literatures. DSSC with Ru-bipyridyl complexes (N3 and N719), and the black ruthenium dye have achieved power conversion efficiencies up to 11.2% and 10.4%, respectively. However, the Ru-dyes are facing the problem of manufacturing costs and environmental issues. In order to obtain even cheaper photosensitizers for DSSC, metal-free organic photosensitizers are strongly desired. Metal-free organic dyes offer superior molar extinction coefficients, low cost, and a diversity of molecular structures, compared to conventional Ru-dyes. Recently, novel photosensitizers such as coumarin, merocyanine, cyanine, indoline, hemicyanine, triphenylamine, dialkylaniline, bis(dimethylfluorenyl)-aminophenyl, phenothiazine, tetrahydroquinoline, and carbazole based dyes have achieved solar-to-electrical power conversion efficiencies up to 5-9%. On the other hand, organic dye molecules have large ${\pi}$-conjugated planner structures which would bring out strong molecular stacking in their solid-state and poor solubility in their media. It was well known that the molecular stacking of organic dyes could reduce the electron transfer pathway in opto-electronic devices, significantly. In this paper, we have studied on synthesis and characterization of dendritic organic dyes with different number of electron acceptor/anchoring moieties in the end of dendrimer. The photovoltaic performances and the incident photon-to-current (IPCE) of these dyes were measured to evaluate the effects of the dendritic strucuture on the open-circuit voltage and the short-circuit current.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.117.2-117.2
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• 2011

Since Gratzel and co-workers developed a new type of solar cell based on the nanocrystalline TiO2 electrode, dye-sensitized solar cells (DSSCs) have attracted considerable attention on account of their high solar energy-to-conversion efficiencies (11%), their easy manufacturing process with low cost production compared to conventional p-n junction solar cells. The mechanism of DSSC is based on the injection of electrons from the photoexcited dye into the conduction band of nanocrystalline TiO2. The oxidized dye is reduced by the hole injection process from either the hole counter or electrolyte. Thus, the electronic structures, such as HOMO, LUMO, and HOMO-LUMO gap, of dye molecule in DSSC are deeply related to the electron transfer by photoexcitation and redox potential. To date, high performance and good stability of DSSC based on Ru-dyes as a photosensitizer had been widely addressed in the literatures. DSSC with Ru-bipyridyl complexes (N3 and N719), and the black ruthenium dye have achieved power conversion efficiencies up to 11.2% and 10.4%, respectively. However, the Ru-dyes are facing the problem of manufacturing costs and environmental issues. In order to obtain even cheaper photosensitizers for DSSC, metal-free organic photosensitizers are strongly desired. Metal-free organic dyes offer superior molar extinction coefficients, low cost, and a diversity of molecular structures, compared to conventional Ru-dyes. Recently, novel photosensitizers such as coumarin, merocyanine, cyanine, indoline, hemicyanine, triphenylamine, dialkylaniline, bis(dimethylfluorenyl)-aminophenyl, phenothiazine, tetrahydroquinoline, and carbazole based dyes have achieved solar-to-electrical power conversion efficiencies up to 5-9%. On the other hand, organic dye molecules have large ${\pi}$-conjugated planner structures which would bring out strong molecular stacking in their solid-state and poor solubility in their media. It was well known that the molecular stacking of organic dyes could reduce the electron transfer pathway in opto-electronic devices, significantly. In this paper, we have studied on synthesis and characterization of dendritic organic dyes with different number of electron acceptor/anchoring moieties in the end of dendrimer. The photovoltaic performances and the incident photon-to-current (IPCE) of these dyes were measured to evaluate the effects of the dendritic strucuture on the open-circuit voltage and the short-circuit current.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.128-132
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• 2004

Short wave infrared (SWIR) photovoltaic devices have been fabricated from metal organic vapour phase epitaxy (MOVPE) grown n- on p- HgCdTe films on GaAs substrates. The MOVPE grown films were processed into mesa type discrete devices with wet chemical etching employed for meas delineation and ZnS surface passivatlon. ZnS was thermally evaporated from effusion cell in an ultra high vacuum (UHV) chamber. The main features of the ZnS deposited from effusion cell in UHV chamber are low fixed surface charge density, and small hysteresis. It was found that a negative flat band voltage with -0.6 V has been obtained for Metal Insulator Semiconductor (MIS) capacitor which was evaporated at $910^{\circ}C$ for 90 min. Current-Voltage (I-V) and temperature dependence of the I-V characteristics were measured in the temperature range 80 - 300 K. The Zero bias dynamic resistance-area product ($R_{0}A$) was about $7500{\Omega}-cm^{2}$ at room temperature. The physical mechanisms that dominate dark current properties in the HgCdTe photodiodes are examined by the dependence of the $R_{0}A$ product upon reciprocal temperature. From theoretical considerations and known current expressions for thermal and tunnelling process, the device is shown to be diffusion limited up to 180 K and g-r limited at temperature below this.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.93-98
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• 2013

In this paper, four conducting polymers (poly[(N-butyl-phenothiazine)-sulfide] (PBPS), poly[(N-hexyl-phenothiazine)-sulfide] (PHPS), poly[(N-decyl-phenothiazine)-sulfide] (PDPS), and poly[(N-(2-ethylhexyl)-phenothiazine)-sulfide] (PEHPS)) were synthesized with a high temperature and high pressure reaction. The structures of synthesized polymers were confirmed by $^1H-NMR$ and characterized by UV-Vis, cyclic voltammetry, and GPC. From the UV-Vis absorption spectra, the ${\lambda}_{max}$ values of PBPS, PHPS, PDPS, and PEHPS were 338, 341, 340, and 334 nm, respectively and their optical band gaps were 3.11, 3.13, 3.16, and 3.05 eV, respectively. To evaluate the feasible applicability as a photovoltaic cell, the devices composed of for example, ITO/PEDOT : PSS/polymer (PBPS, PDPS) : $PC_{71}BM$ (1 : 3, w/w)/$BaF_2$/Ba/Al were fabricated using the blends of the PBPS and PDPS as a donor, and $PC_{71}BM$ as an acceptor. Then, the power conversion efficiencies (PCE) of devices were estimated as 0.076% of PBPS and 0.136% of PDPS by solar simulator.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.221-221
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• 2012

Small-molecule organic photovoltaic cells have recently attracted growing attention due to their potential for the low-cost fabrication of flexible and lightweight solar modules. The PVP/Ag nanoparticles were synthesized by the reaction of poly vinylpyrrolidone (PVP) and silver nitrate at $150^{\circ}C$. In the reaction, the size of the nanoparticles was controlled by relative mole fractions between PVP and Ag. The PVP/Ag nanoparticles with various sizes were then spin coated on the patterned ITO glass prior to the deposition of the PEDOT:PSS hole transport layer. The scattering of the incident light caused by these incorporated nanoparticles resulted in an increase in the path length of the light through the active layer and hence the enhancement of the light absorption. This scattering effect increased as the size of the nanoparticles increased, but it was offset by the decrease in total transmittance caused by the non-transparent nanoparticles. As a result, the maximum power conversion efficiency, 0.96% which was the value enhanced by 14% compared to the cell without incorporation of nanoparticles, was obtained when the mole fraction of PVP:Ag was 24:1 and the size of the nanoparticles was 20~40 nm.

• 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.

• Ceramist
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• v.23 no.2
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• pp.145-165
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• 2020

Halide perovskites are promising photovoltaic materials due to their excellent optoelectronic properties like high absorption coefficient, low exciton binding energy and long diffusion length, and single-junction solar cells consisting of them have shown a high certified efficiency of 25.2%. Despite of high efficiency, perovskite photovoltaics show poor stability under actual operational condition, which is the mostly critical obstacle for commercialization. Given that the stability of the perovskite devices is significantly affected by charge-transporting layers, the use of inorganic charge-transporting layers with better intrinsic stability than the organic counterparts must be beneficial to the enhanced device reliability. In this review article, we summarized a number of studies on the inorganic charge-transporting layers of the perovskite solar cells, especially focusing on their effects on the enhanced device reliability.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.376-376
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• 2011

I-III-VI2 chalcopyrite compounds, particularly copper, indium, gallium selenide(Cu(InxGa1-x)Se2, CIGS), are effective light-absorbing materials in thin-film solar application. They are direct band-gap semiconductors with correspondingly high optical absorption coefficients. Also they are stable under long-term excitation. CIS (CIGS) solar cell reached conversion efficiencies as high as 19.5%. Several methods to prepare CIS (CIGS) absorber films have been reported, such as co-evaporation, sputtering, selenization, and electrodeposition. Until now, co-evaporation is the most successful technique for the preparation of CIS (CIGS) in terms of solar efficiency, but it seems difficult to scale up. CIS solar cells have been hindered by high costs associated with a fabrication process. Therefore, inorganic colloidal ink suitable for a scalable coating process could be a key step in the development of low-cost solar cells. Here, we will present the preparation of CIS photo absorption layer by a solution process using novel metal precursors. Chalcopyrite copper indium diselenide (CuInSe2) nanocrystals ranging from 5 to 20nm in diameter were synthesized by arrested precipitation in solution. For the fabrication of CIS photo absorption layer, the CuInSe2 colloidal ink was prepared by dispersing in organic solvent and used to drop-casting on molybdenum substrate. We have characterized the nanoparticless and CIS layer by XRD, SEM, TEM, and ICP.