• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.348-348
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• 2016

Low dark current (off-current) and high photo current are both essential for a solution processed organic photodetector (OPD) to achieve high photo-responsivity. Currently, most OPDs utilize a bulk heterojunction (BHJ) photo-active layer that is prepared by the one-step deposition of a polymer:fullerene blend solution. However, the BHJ structure is the main cause of the high dark current in solution processed OPDs. It is revealed that the detectivity and spectral responsivity of the OPD can be improved by utilizing a photo-active layer consisting of an interdiffused polymer/fullerene bilayer (ID-BL). This ID-BL is prepared by the sequential solution deposition (SqD) of poly(3-hexylthiophene) (P3HT) and [6,6] phenyl C61 butyric acid methyl ester (PCBM) solutions. The ID-BL OPD is found to prevent undesirable electron injection from the hole collecting electrode to the ID-BL photo-active layer resulting in a reduced dark current in the ID-BL OPD. Based on dark current and external quantum efficiency (EQE) analysis, the detectivity of the ID-BL OPD is determined to be $7.60{\times}1011$ Jones at 620 nm. This value is 3.4 times higher than that of BHJ OPDs. Furthermore, compared to BHJ OPDs, the ID-BL OPD exhibited a more consistent spectral response in the range of 400 - 660 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.444-444
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• 2008

For the polymer tandem cell, simple and advantaged solution-based method to electron transport intermediate layer is presented which are composed $TiO_2$ nanoparticles. Device were based on a regioregular Poly(3-hexylthiophene)(P3HT) and [6,6]-phenyl $C_{61}$ butyric acid methyl ester($PC_{60}BM$) blend as a donor and acceptor bulk-heterojunction. For the middle electrode interlayer, the $TiO_2$ nanoparticles were well dispersed in ethanol solution and formed thin layer on the P3HT:PCBM charge separation layer by spin coating. The layer serves as the electron transport layer and divides the polymer tandem solar cell. The open-circuit voltage (Voc) for the polymer tandem solar cells was closed to the sum of those of individual cells.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.108-109
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• 2011

유기태양전지를 제작 시에 요구되는 것 중 하나는 active layer의 thermal annealing이다. Thermal thermal annealing 없이는 P3HT의 self-organization이 잘 이뤄지지 않아 비정질의 모습을 보인다. 또한 low band-gap이나 열에 취약한 물질을 사용 시에 태양전지 효율이 낮아지게 된다. 이 점을 착안하여 Active layer에 사용되는 유기용매의 solvent vapor pressure 차이를 이용하여 co-solvent가 되도록 mixing하여, co-solvent로 poly(3-hexylthiopene)(P3HT):[6,6] - phenyl $C_{61}$-butyric acid methyl ester (PCBM)를 blending 하여 active layer로 사용하였으며, 유기태양전지 디바이스 제작 결과 thermal thermal annealing 없이 2.8%까지 도달하였다. X-Ray Diffraction(XRD)과 Atomic Force Microscopy(AFM)를 통하여 P3HT의 결정화가 이루어 졌음을 확인하고 이를 통해 active layer의 thermal annealing이 없이도 P3HT의 self-organization이 이뤄짐을 알 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.301-301
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• 2010

In order to enhance the efficiency of the organic solar cells, the effects of plasma surface treatment with using $CF_4$ and $O_2$ gas on the anode ITO were studied. The polymer solar cell devices were fabricated on ITO glasses an active layer of P3HT (poly-3-hexylthiophene) and PCBM ([6,6]-phenyl C61-butyric acid methyl ester) mixture, without anode buffer layer, such as PEDOT:PSS layer. The metallic electrode was formed by thermally evaporated Al. Before the coating of organic layers, ITO surface was exposed to plasma made of $CF_4$ and $O_2$ gas, with/without heat treatment. In order to identify the effect the surface treatment, the current density and voltage characteristics were measured by solar simulator and the chemical composition of plasma treated ITO surface was analyzed by using X-ray photoelectron spectroscopy(XPS). In addition, the work function of the plasma treated ITO surface was measured by using ultraviolet photoelectron spectroscopy(UPS). The effects of plasma surface treatment can be attributed to the removal organic contaminants of the ITO surface, to the improvement of contact between ITO and buffer layer, and to the increase of work function of the ITO.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.63-67
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• 2010

The organic solar cells with Glass/ITO/PEDOT:PSS/P3HT:PCBM/Al structure were fabricated using regioregular poly (3-hexylthiophene) (P3HT) polymer:(6,6)- phenyl $C_{61}$-butyric acid methyl ester (PCBM) fullerene polymer as the bulk hetero-junction layer. The P3HT and PCBM as the electron donor and acceptor materials were spin casted on the indium tin oxide (ITO) coated glass substrates. The optimum mixing concentration ratio of photovoltaic layer was found to be P3HT:PCBM = 4:4 in wt%, indicating that the short circuit current density ($J_{SC}$), open circuit voltage ($V_{OC}$), fill factor (FF) and power conversion efficiency (PCE) values were about 4.7 $mA/cm^2$, 0.48 V, 43.1% and 0.97%, respectively. To investigate the effects of the post annealing treatment, as prepared organic solar cells were post annealed at the treatment time range from 5min to 20min at $150^{\circ}C$. $J_{SC}$ and $V_{OC}$ increased with increasing the post annealing time from 5min to 15min, which may be originated from the improvement of the light absorption coefficient of P3HT and improved ohmic contact between photo voltaic layer and Al electrode. The maximum $J_{SC},\;V_{OC}$, FF and PCE values of organic solar cell, which was post annealed for 15min at $150^{\circ}C$, were found to be about 7.8 $mA/cm^2$, 0.55 V, 47% and 2.0%, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.217-217
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• 2012

Solution-processed tungsten oxide thin film with thickness of about 30 nm is prepared from ammonium tungstate. This layer is introduced into the interface between the poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) layer and the ITO electrode to be used as an electron blocking layer. The annealed tungsten oxide thin films at $150^{\circ}C$ and $300^{\circ}C$ show amorphous phase, while the $400^{\circ}C$ -annealed tungsten oxide film shows crystalline phase. At $150^{\circ}C$ annealing temperature, the conversion efficiency is significantly improved from 0.71% to 1.42% as the condition is changed from vacuum to air atmosphere, which is related to oxidation state of tungsten in amorphous phase. For the air annealing condition, the conversion efficiency is further increased from 1.42% to 2.01% as the temperature is increased from $150^{\circ}C$ to $300^{\circ}C$, which is mainly due to the removal of the chemisorbed water. However, a slight deterioration in photovoltaic performance is observed when the temperature is increased to $400^{\circ}C$, which is ascribed to poor electron blocking ability due to the formation of crystalline phase. It is concluded that $W^{6+}$ oxidation state and amorphous nature in tungsten oxide interlayer is essential for blocking electron effectively from the active layer to the ITO electrode.