Synergistic photocurrent addition in hybrid quantum dot: Bulk heterojunction solar cells

Kim, Gi-Hwan,Walker, Bright,Zhitomirsky, David,Heo, Jungwoo,Ko, Seo-Jin,Park, Jongnam,Sargent, Edward H.,Young Kim, Jin Elsevier 2015 Nano energy Vol.13 No.-

<P><B>Abstract</B></P> <P>We investigate the effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs). The PbS QD layer is able to function as a photosensitizing layer to improve short circuit current density (<I>J</I> <SUB>SC</SUB>) and power conversion efficiency (PCE) by exploiting solar flux in the near infrared region up to 1100nm. The increase in <I>J</I> <SUB>SC</SUB> is well represented by changes observed in the external quantum efficiency of devices with and without the PbS QD layer, including the region of the first exciton transition where only the PbS QD layer absorbs. Remarkably, enhanced performance was observed in QD-OSCs consisting of just a 13nm thick PbS QD layer and 150nm PTB7:PC<SUB>71</SUB>BM layer, exhibiting a <I>J</I> <SUB>SC</SUB> of 17.0mAcm<SUP>−2</SUP>, and PCE of 8.30% (8.58% for champion device) compared to reference devices without PbS QD which produced a <I>J</I> <SUB>SC</SUB> of 15.4mAcm<SUP>−2</SUP> and PCE of 7.56%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have fabricated hybrid solar cells using a PbS QD layer and PTB7/PC<SUB>71</SUB>BM layer. </LI> <LI> The device is built on PTB7:PC<SUB>71</SUB>BM bulk heterojunction and a PbS QD layer. </LI> <LI> The PbS QD layer acts as a photosensitizing layer to improve the device performance. </LI> <LI> Additional photocurrent leads to enhancement in performance in hybrid solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs) was investigated. The PbS QD layer is able to function as a photosensitizing layer with PTB7/PC<SUB>71</SUB>BM bulk heterojunction to improve short circuit current density from 15.4mAcm<SUP>−2</SUP> to 17.0mAcm<SUP>−2</SUP> and power conversion efficiency from 7.56% to 8.30%. </P> <P>[DISPLAY OMISSION]</P>

Quantum Dot Sensitized Solar Cells Based on TiO2/AgInS2

Sachin A. Pawar,정재필,Dipali S. Patil,Vivek M. More,Rochelle S. Lee,신재철,최원준 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.10

Quantum dot heterojunctions with type-II band alignment can efficiently separate photogenerated electron-hole pairs and, hence, are useful for solar cell studies. In this study, a quantum dot sensitized solar cell (QDSSC) made of TiO2/AgInS2 is achieved to boost the photoconversion efficiency for the TiO2-based system by varying the AgInS2 layer’s thickness. The TiO2 nanorods array film is prepared by using a simple hydrothermal technique. The formation of a AgInS2 QD-sensitized TiO2-nanorod photoelectrode is carried out by successive ionic layer adsorption and reaction (SILAR) technique. The effect of the QD layer on the performance of the solar cell is studied by varying the SILAR cycles of the QD coating. The synthesized electrode materials are characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy and solar cell performances. The results indicate that the nanocrystals have effectively covered the outer surfaces of the TiO2 nanorods. The interfacial structure of quantum dots (QDs)/TiO2 is also investigated, and the growth interface is verified. A careful comparison between TiO2/AgInS2 sensitized cells reveals that the trasfer of electrons and hole proceeds efficiently, the recombination is suppressed for the optimum thickness of the QD layer and light from the entire visible spectrum is utilised. Under AM 1.5G illumination, a high photocurrent of 1.36 mAcm−2 with an improved power conversion efficiency of 0.48% is obtained. The solar cell properties of our photoanodes suggest that the TiO2 nanorod array films co-sensitized by AgInS2 nanoclusters have potential applications in solar cells.

Graphene transparent conductive electrodes doped with graphene quantum dots-mixed silver nanowires for highly-flexible organic solar cells

Shin, Dong Hee,Seo, Sang Woo,Kim, Jong Min,Lee, Ha Seung,Choi, Suk-Ho Elsevier 2018 Journal of alloys and compounds Vol.744 No.-

<P><B>Abstract</B></P> <P>Recent active studies on flexible photovoltaic cells strongly call for matchable flexible transparent electrodes. Graphene (GR) is one of the promising candidates as transparent conductive electrodes (TCEs) for flexible photovoltaic cells, but high sheet resistance of GR limits the efficiency of the cells. Here, we first fabricate GR TCEs doped with graphene quantum dots (GQDs)-mixed silver nanowires (Ag NWs) on polyethylene terephthalate substrates for highly-flexible organic solar cells (OSCs). With increasing doping concentration of GQDs to 0.03 g/L, the sheet resistance of the Ag NWs/GR TCE decreases to ∼92 Ω/sq whilst its work function increases to ∼4.53 eV, resulting in 3.66% power-conversion efficiency (PCE). In addition, the GQDs enhance the bending flexibility of the Ag NWs/GR TCEs, thereby maintaining the initial PCE of the OSCs over 90% even after 1000 bending cycles at a curvature radius of 4 mm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First use of graphene transparent conductive electrodes doped with graphene quantum dots-mixed silver nanowires. </LI> <LI> Graphene quantum dots make the doped graphene more suitable for anode electrodes of organic solar cells. </LI> <LI> Graphene quantum dots enhance the power-conversion efficiency of organic solar cells to 3.66%. </LI> <LI> Graphene quantum dots enhance the bending flexibility of organic solar cells. </LI> </UL> </P>

박막 실리콘 태양전지의 광열화현상 연구: 비정질 실리콘 태양전지 및 나노양자점 실리콘 박막 태양전지

김가현 한국태양에너지학회 2019 한국태양에너지학회 논문집 Vol.39 No.1

Light induced degradation is one of the major research challenges of hydrogenated amorphous silicon related thin film silicon solar cells. Amorphous silicon shows creation of metastable defect states, originating from elevated concentration of dangling bonds during light exposure. The metastable defect states work as recombination centers, and mostly affects quality of intrinsic layer in solar cells. In this paper we present results of light induced degradation in thin film silicon solar cells and discussion on physical origin, mechanism and practical solutions of light induced degradation in thin film silicon solar cells. In-situ light-soaking IV measurement techniques are presented. We also present thin film silicon material with silicon nano-quantum dots embedded within amorphous matrix, which shows superior stability during light-soaking. Our results suggest that solar cell using silicon nano-quantum dots in abosrber layer shows superior stability under light soaking, compared to the conventional amorphous silicon solar cell.

Oxygen annealing of the ZnO nanoparticle layer for the high-performance PbS colloidal quantum-dot photovoltaics

Yang, Jonghee,Lee, Jongtaek,Lee, Junyoung,Yi, Whikun Elsevier 2019 Journal of Power Sources Vol.421 No.-

<P><B>Abstract</B></P> <P>Though numerous researches regarding the influence of annealing atmospheric condition of ZnO have been carried out, the impact of annealing atmosphere on the carrier transporting properties and the performance of the ZnO-based optoelectronics has not been well-established. Here, the effects of annealing atmosphere (<I>i.e.</I>, N<SUB>2</SUB>, ambient air, and O<SUB>2</SUB>) used to generate ZnO nanoparticle (NP) layers are elucidated. The chemical nature of ZnO layers, especially the amount of oxygen vacancies in ZnO NPs, is modulated by the annealing atmosphere. As the composition of O<SUB>2</SUB> gas increases in the annealing atmosphere, a notable reduction of oxygen vacancies of ZnO NPs and electron mobility enhancement are observed, indicating that O<SUB>2</SUB> gas contributes to a reduction of surface defects on ZnO NPs during the annealing process. In addition, trap-filling by reduced oxygen vacancies of air- and O<SUB>2</SUB>-annealed ZnO layers, induces the enhanced built-in potential in colloidal quantum-dot photovoltaic (CQDPV) devices. As expected, PbS CQDPVs with an air- and O<SUB>2</SUB>-annealed ZnO layer demonstrate significantly improved power conversion efficiencies than CQDPVs with an N<SUB>2</SUB>-annealed ZnO layer. Further analysis shows that the interfacial recombination is reduced for CQDPVs with an air- and O<SUB>2</SUB>-annealed ZnO layer due to the reduced trap states of ZnO NPs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of annealing atmosphere on the surface defects of ZnO were elucidated. </LI> <LI> PbS quantum dot solar cell with an O<SUB>2</SUB>-annealed ZnO showed enhanced open-circuit voltage. </LI> <LI> As increasing O<SUB>2</SUB> concentration during annealing, the defects of ZnO were passivated. </LI> <LI> Defect passivation suppressed interfacial charge recombination in the solar cell. </LI> <LI> The suppression of charge recombination induced the improved V<SUB>OC</SUB> of the solar cell. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Silica/Alumina Monolith Passivation layers for Improving Photovoltaic Performances of Copper-Indium-Selenide Quantum Dot-Sensitized Solar Cells

이아름,백운혁,현택환,김재엽 한국공업화학회 2021 한국공업화학회 연구논문 초록집 Vol.2021 No.1

Preparation of copper sulfide electrocatalyst using electrodeposited Cu-Zn alloy for quantum dot-sensitized solar cells

채지영,( Vu Hong Vinh Quy ),( Elayappan Vijayakumar ),( Anthuvan Rajesh ),안광순 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Quantum dot-sensitized solar cells (QDSSCs) are a reliable renewable energy source. A QDSSC is assembled with the components in the following order: FTO/TiO2/QD/polysulfide electrolyte/CE/FTO. Recently, multiple efforts have been made to increase the power conversion efficiency of by modifying the materials by optimize chemical and physical properties. In QDSSCs, the counter electrodes (CEs) plays a key role in completing the electrical circuit and in the regeneration of sulfur redox couple through a reduction process. Among the CE materials, copper(I) sulfide (Cu2S) is a promising alternative to Pt CE, primarily due to its favorable electrochemical properties in the S2-/Sn2- redox couple, low cost, and high stability compared to other. In this study, we have reported Cu2S CE deposited Cu-Zn alloy on FTO and removed Zn using HCl after sulfurization. We simply increased surface area of CEs by removing Zn. These samples exhibited better electrocatalytic activity than FTO/Cu2S CEs.

나노튜브 전극 기반 양자점 감응 태양전지 구현을 위한 투명한 상대전극

김재엽,Kim, Jae-Yup 한국표면공학회 2019 한국표면공학회지 Vol.52 No.1

Anodic oxidized $TiO_2$ nanotube arrays are promising materials for application in photoelectrochemical solar cells as the photoanode, because of their attractive properties including slow electron recombination rate, superior light scattering, and smooth electrolyte diffusion. However, because of the opacity of these nanotube electrodes, the back-side illumination is inevitable for the application in solar cells. Therefore, for the fabrication of solar cells with the anodic oxidized nanotube electrodes, it is required to develop efficient and transparent counter electrodes. Here, we demonstrate quantum dot-sensitized solar cells (QDSCs) based on the nanotube photoanode and transparent counter electrodes. The transparent counter electrodes based on Pt electrocatalysts were prepared by a simple thermal decomposition methods. The photovoltaic performances of QDSCs with nanotube photoanode were tested and optimized depending on the concentration of Pt precursor solutions for the preparation of counter electrodes.

The role of ZnO-coating-layer thickness on the recombination in CdS quantum-dot-sensitized solar cells

Choi, H.,Kim, J.,Nahm, C.,Kim, C.,Nam, S.,Kang, J.,Lee, B.,Hwang, T.,Kang, S.,Choi, D.J.,Kim, Y.H.,Park, B. Elsevier 2013 Nano energy Vol.2 No.6

To prevent recombination at the interface of TiO<SUB>2</SUB>/polysulfide-electrolyte, a ZnO layer was deposited on a TiO<SUB>2</SUB> electrode. The optimized ZnO-coated solar cell exhibited a ~32% increase in the power-conversion efficiency compared to the bare cell. The coating layer acts as an energy barrier, which plays an important role in reducing the charge recombination from the TiO<SUB>2</SUB> electrode to the electrolyte. Moreover, CdS quantum-dot adsorption was enhanced by employing the ZnO-coated layer. The thicker ZnO layer (more than 8-cycle deposition), however, led to a less porous electrode, as confirmed by electrolyte diffusivity, and also deteriorated the cell efficiency by introducing defect states verified by electron lifetime and chronoamperometric reduction current.

Enhanced spectral response of CIGS solar cells with anti-reflective subwavelength structures and quantum dots

Jeong, Ho-Jung,Kim, Ye-Chan,Lee, Soo Kyung,Yun, Ju-Hyung,Jang, Jae-Hyung Elsevier 2019 Solar energy materials and solar cells Vol.194 No.-

<P><B>Abstract</B></P> <P>A cover glass integrated with subwavelength structures (SWSs) and quantum dots (QDs) was realized to enhance the spectral response of Cu(In<SUB>1-x</SUB>Ga<SUB>x</SUB>)Se<SUB>2</SUB> (CIGS) thin film solar cells. The nanoscale SWSs was produced on the front and backside of cover glass using the self-masked etching method. The fabricated SWSs-integrated glass (SIG) exhibited superior anti-reflective properties over a broad wavelength range and a broad range of incident angle. The average transmittance of the single and double-sided SIG was increased from 92.4% to 95.2% and 97.8% in the wavelength range between 300 and 1200 nm, as compared to that of a flat surface glass. QDs were formed between the fabricated SIG and ZnO layer to act as a luminescent down-shifting (LDS) layer. A large amount of light can pass through the SIG, enhancing the efficiency of the LDS by improving light absorption and lowering reflection. After successful integration of the SIG with QDs (QD/SIG) on top of the CIGS devices, photovoltaic performance was significantly improved. The power conversion efficiency of the CIGS devices integrated with QD/double-sided SIG was improved by 7.41%, compared with that of a reference device (without QD/cover glass). The efficiency improvement is attributed to the enhanced solar energy harvesting by the efficient LDS and the minimized surface reflection loss.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CIGS thin film solar cells with broadband spectral response were investigated. </LI> <LI> Subwavelength structures (SWS) with high aspect ratio were realized on the surface of cover glass using self-masked etching. </LI> <LI> SWSs-integrated glass coated with quantum dots (QDs) provide improved spectral response in the CIGS thin film solar cells. </LI> <LI> By employing double sided SWSs-integrated glass and QDs, the efficiency of CIGS solar cell was improved by 7.41%. </LI> </UL> </P>