Browsing by Author "Lin, Yi-Cheng"

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10% Efficiency Hybrid GaAs/PEDOT:PSS Solar Cells with Monolayer Graphene
(2014-01-01)
Cheng, Kai-Yuan
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Pan, Huai-Te
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Yu, Shu-Cheng
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Weng, Wei-Sheng
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Lai, Yi-Chun
The development of solution-processed hybrid organic-inorganic heterojunction solar cells have provoked increasing research effort due to potential to significantly reduce the fabrication cost of semiconductor solar cells while maintaining the high power conversion efficiency (PCE). With a recent record of GaAs solar cells achieving 28.8% via a wafer lift-off technique, hybrid organic/GaAs solar cells can offer an alternative route to provide more affordable solar power than current semiconductor technologies. In this work, we demonstrate the hybrid devices based on a conductive polymer poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) directly spun-cast on planar gallium arsenide materials. While still lacking for optimized antireflection, the PCE of the best performing device can achieve nearly 10% by introducing the monolayer graphene as transparent electrode. The current progress presents 2-fold enhancement in comparison to a previous record at 5% based on GaAs nanowire templates.
Hybrid Carbon Nanotube/Silicon Schottky Junction Solar Cells
(2016-01-01)
Chen, Sih-Han
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Lai, Yi-Chun
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Tsai, Pei-Ting
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Lin, Yi-Cheng
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Lin, Yan-Nan
In this work, highly transparent and conductive multi-wall-carbon nanotubes (MW-CNTs) are employed to realize solution-processed, hybrid silicon (Si) Schottky -junction solar cells. We first describe the optimization of device structures on silicon wafers with nanowire and micro-pyramidal surface textures, and compare the device characteristics with those of hybrid cells based on Si and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS). The optimized processing conditions include the length of silicon nanowires, the annealing temperature, and the shading ratio of the frontal silver grids. It is found that the hybrid CNT cells outperform the hybrid PEDOT: PSS counterpart under individually optimized processing conditions due to better transparency and conductivity of CNTs than PEDOT: PSS. The best hybrid CNT cells, fabricated using a 14% grid shield ratio, 150 degrees C annealing temperature, and 150nm nanowire length, achieve a PCE of 11.90% and 13.82% in micro-pyramid and nanowire (NW) textured silicon, respectively, in contrast to 7.43% and 12.96% for hybrid PEDOT: PSS cells. To control the rear surface recombination, we further employ two solution-processed, small-molecule materials, Tris(8-hydroxyquinolinato) aluminium (Alq(3)) and 1,3-bis(2-(4-tert-butylphenyl)-1,3,4-oxadiazol- 5-yl) benzene (OXD-7) via a blade-coating technique between the silicon wafer and aluminum electrode. As a result, the PCE of hybrid CNT/Si NW solar cells is enhanced to 13.92% and 14.41% with the insertion of the Alq3 and OXD-7 rear interlayer, respectively. With the high power conversion efficiency (PCE), manufacturing Si-based solar cells at temperatures below 150 degrees C without high vacuum conditions not only significantly lowers the fabrication cost, but also enables the use of ultrathin substrates to save on the material cost for the future.
Profile and interface control of hybrid organic-silicon nanorod solar cells
(2015)
Chen, Yu-Cheng
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Lin, Yi-Cheng
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Yu, Liang-Chian
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Yu, Peichen
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光電工程學系
Hybrid organic-silicon solar cells are promising candidates for next-generation photovoltaics due to their low fabrication cost and scalable roll-to-roll processes. However, the power conversion efficiency (PCE) cannot compete with those of traditional silicon solar cells yet mostly due to surface reflection and interface recombination losses. In this work, we investigate the sidewall profile and interface defects of silicon nanorod templates, fabricated by means of polystyrene lithography, followed by metal-assisted chemical etch (MACE), for hybrid photovoltaics. The control of nanorod sidewall profile is important to organic surface coverage, as well as optical absorption for thin-silicon substrates, whereas the control of interface defects is important to boost the open-circuit voltage of hybrid devices. We systematically compared the optical and electrical characteristics of hybrid organic-silicon nanorod (Si NR) devices made with different noble metal etching catalysts: gold (Au) and silver (Ag), which result in different surface morphologies. The preliminary results show that Si NRs made of Ag catalysts have lower interface defects than those of Au catalysts. After passivated by 10nm-Al2O3, the minority carrier lifetime is 157 mu sec (A g) versus 29 mu sec (Au). Moreover, a PCE of 11.9% is achieved with the hybrid solar cells using Ag catalysts without any post-etching surface treatment, where the short-circuit current is as high as >34 mA/cm(2) enhanced by the nearly periodical pillar arrangement. The Si NR template made with Au catalysts requires further damage removal etch (DRE), which also lead to a high PCE of 11.37% and Jsc of similar to 34 mA/cm(2) . Currently optimization of device structure and fabrication technique is still in process and more experimental and simulation data will be presented.
Rear interface engineering of hybrid organic-silicon nanowire solar cells via blade coating
(2016-01-25)
Lai, Yi-Chun
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Chang, Yu-Fan
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Tsai, Pei-Ting
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Chang, Jan-Kai
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Tseng, Wei-Hsuan
In this work, we investigate blade-coated organic interlayers at the rear surface of hybrid organic-silicon photovoltaics based on two small molecules: Tris(8-hydroxyquinolinato) aluminium (Alq(3)) and 1,3-bis(2-(4-tert- butylphenyl)-1,3,4-oxadiazol-5-yl) benzene (OXD-7). In particular, soluble Alq3 resulting in a uniform thin film with a root-mean-square roughness < 0.2nm is demonstrated for the first time. Both devices with the Alq3 and OXD-7 interlayers show notable enhancement in the open-circuit voltage and fill-factor, leading to a net efficiency increase by over 2% from the reference, up to 11.8% and 12.5% respectively. The capacitance-voltage characteristics confirm the role of the small-molecule interlayers resembling a thin interfacial oxide layer for the Al-Si Schottky barrier to enhance the built-in potential and facilitate charge transport. Moreover, the Alq3 interlayer in optimized devices exhibits isolated phases with a large surface roughness, in contrast to the OXD-7 which forms a continuous uniform thin film. The distinct morphological differences between the two interlayers further suggest different enhancement mechanisms and hence offer versatile functionalities to the advent of hybrid organic-silicon photovoltaics. (C)2016 Optical Society of America
Reduced hole injection barrier for achieving ultralow voltage polymer space-charge-limited transistor with a high on/off current ratio
(2009-11-16)
Chao, Yu-Chiang
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Lin, Yi-Cheng
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Dai, Min-Zhi
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Zan, Hsiao-Wen
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Meng, Hsin-Fei
Vertical polymer space-charge limited transistor (SCLT) operated with an ultralow voltage is demonstrated. The influence of aging effect of the oxygen plasma treated indium tin oxide electrode on the hole injection barrier and on the transistor characteristics is investigated. By reducing the hole injection barrier, the on/off ratio as high as 10(4) is obtained at a collector to emitter voltage as low as -0.84 V. The low operation voltage is crucial to the development of low-power large-area polymer transistor array. Inverter characteristics are also demonstrated by connecting a SCLT with a load resistor.
Solution p-doped fluorescent polymers for enhanced charge transport of hybrid organic-silicon nanowire photovoltaics
(2016-07)
Tsai, Pei-Ting
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Li, Ming-Chin
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Lai, Yi-Chun
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Tseng, Wei-Hsuan
;
Wu, Chih-I
The solution p-type doping of various conjugated polymers and small molecules via blending with tetrafluorotetracyano-quinodimethane (F4-TCNQ) is investigated to facilitate hole transport for hybrid organic-silicon-nanowire solar cells. Among all, the highly-fluorescent conjugated polymers such as poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) demonstrate superior transport characteristics, where both the device fill-factor and power conversion efficiency (PCE) are positively correlated with the doping concentration. The best PCE achieves 13.66% from the device with 30% p-doped PFO, compared to the reference at 12.50%. The enhancement is ascribed to the efficient interfacial charge-carrier recombination with minimal energy losses. A vertically graded doping profile is further revealed with F4-TCNQ molecules preferentially accumulated near the silicon surface. (C) 2016 Elsevier B.V. All rights reserved.