Bulletin of the American Physical Society
2018 Annual Fall Meeting of the APS Ohio-Region Section
Volume 63, Number 15
Friday–Saturday, September 28–29, 2018; University of Toledo, Toledo, Ohio
Session E03: Energy and the Environment |
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Chair: Zhaoning Song, The University of Toledo Room: SU 2591 |
Saturday, September 29, 2018 9:00AM - 9:15AM |
E03.00001: Tuning carrier concentration of SnO2 quantum dot electron transport layers for high-performance planar perovskite solar cells Cong Chen, Guojia Fang, Yanfa Yan Organic-inorganic lead halide perovskite solar cells (PSCs) have shown great potential due to rapid development in power conversion efficiency, which has surpassed 23%. The quality of the electron transport layers (ETLs) and hole transport layers can significantly affect the performance of PSCs. Tin Oxide (SnO2) commonly employed in planar PSCs is a promising material as ETLs. Herein, we facilely synthesize colloidal SnO2 quantum dots (QDs) at room temperature and control the carrier concentration of SnO2 QD ETLs at different annealing temperature to achieve high performance PSCs. By optimizing the electron density of SnO2 QD ETLs, we can achieve a champion stabilized power output of 20.32% for the planar PSCs using triple cation perovskite absorber and 19.73% for those using CH3NH3PbI3-based system. Our results demonstrate the promise of carrier concentration-controlled SnO2 QD ETLs for fabricating stable, efficient and reproducible planar PSCs. |
Saturday, September 29, 2018 9:15AM - 9:30AM |
E03.00002: Enhancing efficiency and stability of perovskite solar cells via a high mobility p-type PbS buffer layer Xiaolu Zheng, Guojia Fang Organo-lead halide perovskite solar cells (PSCs) have attracted tremendous attention owing to their superior photovoltaic properties. However, the device stabilities are still a challenge for the commercialization of PSCs. Spiro-OMeTAD as a widely used hole transport layer (HTL) in PSCs is suffering degradation from the permeate of moisture due to the hygroscopic additive and the presence of pinholes. One approach to diminishing these adverse effects is to insert a buffer layer. Lead sulphide (PbS) is a traditional direct bandgap semiconductor with high hole mobility. We found that when inserting a thin layer of PbS between the metal electrode and spiro-OMeTAD, the PSCs with PbS buffer layer exhibited a better photovoltaic performance and significantly enhanced stability. The superior hole mobility of spiro-OMeTAD/PbS bilayer was considered to be the dominated origin of the device performance improvement. And the hydrophobic nature and dense morphology of PbS enable it to provide an efficient permeation barrier against moisture and metal migration. The champion cell with PbS buffer layer displayed a PCE of 19.58% and maintained almost 100% of its initial PCE after 1000 h stored in ambient air. |
Saturday, September 29, 2018 9:30AM - 9:45AM |
E03.00003: Bifacial CdTe/CdS solar cell using transparent Nanocomposite (CuS)x(ZnS)1-x Thin Film as a Back Contact layer Kamala Khanal Subedi, Ebin Bastola, Indra Subedi, Zhaoning Song, Khagendra P Bhandari, Adam B Phillips, Nikolas Podraza, Michael J. Heben, Randy J. Ellingson We report the properties of earth-abundant p-type transparent conducting nanocomposite (NC) thin film (CuS)x (ZnS)1-x, deposited by a facile and low-cost chemical bath deposition method. Our films of ~45 nm thickness show transparency ~80 % in the visible spectral region (at 550 nm) with compact grains of size < 15 nm. The purpose of fabricating of these wide band gap (~ 2.70 eV) (CuS)x (ZnS)1-x partially transparent thin films was to utilize them as back contacts to CdTe thin film solar cells. Since critical avenues to increased energy yield for CdTe PV technology, such as bifacial cell or tandem cell designs, rely on the need to develop transparent back contact approaches that enable high efficiency and high transparency. Further, when finished with a conductive transparent indium tin oxide (ITO) layer, the high transparency of the NC thin film interface layer enables back illuminated operation of the solar cell. Once optimized, and with an improved interface and bulk CdTe carrier lifetimes, this NC earth-abundant transparent conductor based on Cu, Zn, and S may serve as an effective, inexpensive, low-toxicity back contact layer for a bifacial CdTe solar cell. |
Saturday, September 29, 2018 9:45AM - 10:00AM |
E03.00004: Defect induced absorption in mixed composition perovskite thin films and solar cells Biwas Subedi, Chongwen Li, Lei Guan, Yue Yu, Maxwell Junda, Kiran Ghimire, Prakash Uprety, Yanfa Yan, Nikolas Podraza Device performance, namely, current density (Jsc), open circuit voltage (Voc), fill factor (FF), and efficiency of mixed perovskite (ABX3: A=MA, FA, Cs; B=Pb, Sn; X=I, Br, Cl) thin film solar cells vary with the composition. The major parameters affecting the device performance with varying compositions are crystal structure, phase stability, optical properties, and defect states of the absorber material. Here, we use spectroscopic ellipsometry and photothermal deflection spectroscopy to study to the near-bandgap optical response in terms of the complex refractive index (N = n + ik) of mixed composition perovskite thin films. Sub-bandgap absorption manifests as somewhat well-defined features and Urbach tails below the band gap. Solar cell device performance parameters including Voc, FF, and efficiency as well as external quantum efficiency (EQE) are correlated with the Urbach energies and presence of defect states. |
(Author Not Attending)
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E03.00005: Substrate configuration CdTe solar cells Sandip Singh Bista, Dengbing Li, Suman Rijal, Yanfa Yan Cadmium Telluride (CdTe) thin film solar cells technology is prominent because of optimum theoretical conversion efficiency and low manufacturing cost. CdTe solar cells are fabricated in two configurations namely superstrate and substrate. The latter has many advantages over the former, such as the feasibility to replace rigid glass with flexible metal or polymers, and it is much easier to study the interface. However, substrate configuration still has lots of challenges with record power conversion efficiency of ~14% while superstrate has already reached 22.1%. The issues for substrate configuration is the poor ohmic contact with the substrate. Molybdenum(Mo) is found to be the best back contact because of its high thermal expansion, good conductivity, and adequate reflection. To make better ohmic contact, we worked with various contact layers and found that molybdenum diselenide (MoSe2) boosts better performance for copper (Cu) free CdTe solar cells and a comparative analysis of these contact layers will be presented. The differences between different CdS deposition methods and the effect of heat treatment before and after CdS deposition will also be discussed for substrate configuration. |
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