Charge Sharing and Charge Loss in High-Flux Capable Pixelated CdZnTe Detectors

Kjell A. L. Koch-Mehrin; Sarah L. Bugby; John E. Lees; Matthew C. Veale; Matthew D. Wilson

doi:10.3390/s21093260

Charge Sharing and Charge Loss in High-Flux Capable Pixelated CdZnTe Detectors

Sensors ◽

10.3390/s21093260 ◽

2021 ◽

Vol 21 (9) ◽

pp. 3260

Author(s):

Kjell A. L. Koch-Mehrin ◽

Sarah L. Bugby ◽

John E. Lees ◽

Matthew C. Veale ◽

Matthew D. Wilson

Keyword(s):

Carrier Transport ◽

Hole Transport ◽

Uniform Electric Field ◽

Photon Flux ◽

High Flux ◽

Charge Sharing ◽

Cdte Detector ◽

Charge Loss ◽

Cdznte Detectors ◽

Detector Model

Cadmium zinc telluride (CdZnTe) detectors are known to suffer from polarization effects under high photon flux due to poor hole transport in the crystal material. This has led to the development of a high-flux capable CdZnTe material (HF-CdZnTe). Detectors with the HF-CdZnTe material have shown promising results at mitigating the onset of the polarization phenomenon, likely linked to improved crystal quality and hole carrier transport. Better hole transport will have an impact on charge collection, particularly in pixelated detector designs and thick sensors (>1 mm). In this paper, the presence of charge sharing and the magnitude of charge loss were calculated for a 2 mm thick pixelated HF-CdZnTe detector with 250 μm pixel pitch and 25 μm pixel gaps, bonded to the STFC HEXITEC ASIC. Results are compared with a CdTe detector as a reference point and supported with simulations from a Monte-Carlo detector model. Charge sharing events showed minimal charge loss in the HF-CdZnTe, resulting in a spectral resolution of 1.63 ± 0.08 keV Full Width at Half Maximum (FWHM) for bipixel charge sharing events at 59.5 keV. Depth of interaction effects were shown to influence charge loss in shared events. The performance is discussed in relation to the improved hole transport of HF-CdZnTe and comparison with simulated results provided evidence of a uniform electric field.

Download Full-text

Characterization of the Uniformity of High-Flux CdZnTe Material

Sensors ◽

10.3390/s20102747 ◽

2020 ◽

Vol 20 (10) ◽

pp. 2747 ◽

Cited By ~ 2

Author(s):

Matthew Charles Veale ◽

Paul Booker ◽

Simon Cross ◽

Matthew David Hart ◽

Lydia Jowitt ◽

...

Keyword(s):

Flip Chip ◽

Temporal Stability ◽

Light Sources ◽

High Flux ◽

X Ray Imaging ◽

Science Community ◽

Cdznte Detectors ◽

Photon Science ◽

Synchrotron Light Sources

Since the late 2000s, the availability of high-quality cadmium zinc telluride (CdZnTe) has greatly increased. The excellent spectroscopic performance of this material has enabled the development of detectors with volumes exceeding 1 cm3 for use in the detection of nuclear materials. CdZnTe is also of great interest to the photon science community for applications in X-ray imaging cameras at synchrotron light sources and free electron lasers. Historically, spatial variations in the crystal properties and temporal instabilities under high-intensity irradiation has limited the use of CdZnTe detectors in these applications. Recently, Redlen Technologies have developed high-flux-capable CdZnTe material (HF-CdZnTe), which promises improved spatial and temporal stability. In this paper, the results of the characterization of 10 HF-CdZnTe detectors with dimensions of 20.35 mm × 20.45 mm × 2.00 mm are presented. Each sensor has 80 × 80 pixels on a 250-μm pitch and were flip-chip-bonded to the STFC HEXITEC ASIC. These devices show excellent spectroscopic performance at room temperature, with an average Full Width at Half Maximum (FWHM) of 0.83 keV measured at 59.54 keV. The effect of tellurium inclusions in these devices was found to be negligible; however, some detectors did show significant concentrations of scratches and dislocation walls. An investigation of the detector stability over 12 h of continuous operation showed negligible changes in performance.

Download Full-text

A Cu2O–CuSCN Nanocomposite as a Hole-Transport Material of Perovskite Solar Cells for Enhanced Carrier Transport and Suppressed Interfacial Degradation

ACS Applied Energy Materials ◽

10.1021/acsaem.0c01001 ◽

2020 ◽

Vol 3 (8) ◽

pp. 7572-7579

Author(s):

Jinhyun Kim ◽

Younghyun Lee ◽

Bumjin Gil ◽

Alan Jiwan Yun ◽

Jaewon Kim ◽

...

Keyword(s):

Solar Cells ◽

Carrier Transport ◽

Perovskite Solar Cells ◽

Hole Transport

Download Full-text

Charge carrier transport mechanisms in CdZnTe detectors grown by the vertical Bridgman technique

2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) ◽

10.1109/nssmic.2015.7582267 ◽

2015 ◽

Cited By ~ 1

Author(s):

A. A. Turturici ◽

L. Abbene ◽

G. Gerardi ◽

G. Benassi ◽

D. Calestani ◽

...

Keyword(s):

Charge Carrier ◽

Carrier Transport ◽

Charge Carrier Transport ◽

Transport Mechanisms ◽

Bridgman Technique ◽

Vertical Bridgman ◽

Cdznte Detectors

Download Full-text

Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering

Science Advances ◽

10.1126/sciadv.1501491 ◽

2016 ◽

Vol 2 (4) ◽

pp. e1501491 ◽

Cited By ~ 66

Author(s):

Dong Shi ◽

Xiang Qin ◽

Yuan Li ◽

Yao He ◽

Cheng Zhong ◽

...

Keyword(s):

Crystal Structure ◽

Solar Cells ◽

Charge Carrier ◽

Single Crystals ◽

Carrier Transport ◽

Dye Sensitized Solar Cells ◽

Hole Transport ◽

Transport Pathways ◽

Hole Transporting ◽

Hole Transporting Material

We report the crystal structure and hole-transport mechanism in spiro-OMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene], the dominant hole-transporting material in perovskite and solid-state dye-sensitized solar cells. Despite spiro-OMeTAD’s paramount role in such devices, its crystal structure was unknown because of highly disordered solution-processed films; the hole-transport pathways remained ill-defined and the charge carrier mobilities were low, posing a major bottleneck for advancing cell efficiencies. We devised an antisolvent crystallization strategy to grow single crystals of spiro-OMeTAD, which allowed us to experimentally elucidate its molecular packing and transport properties. Electronic structure calculations enabled us to map spiro-OMeTAD’s intermolecular charge-hopping pathways. Promisingly, single-crystal mobilities were found to exceed their thin-film counterparts by three orders of magnitude. Our findings underscore mesoscale ordering as a key strategy to achieving breakthroughs in hole-transport material engineering of solar cells.

Download Full-text

Hole Transport in Self-Organized Oligosilane Thin Films with Highly Ordered Hopping Sites

MRS Proceedings ◽

10.1557/proc-707-bb10.46.1 ◽

2001 ◽

Vol 707 ◽

Author(s):

H. Okumoto ◽

T. Yatabe ◽

A. Richter ◽

M. Shimomura ◽

A. Kaito ◽

...

Keyword(s):

Thin Films ◽

Transport Properties ◽

Carrier Transport ◽

Hole Mobility ◽

Multilayered Structure ◽

Hole Transport ◽

Conjugated Molecules ◽

Disordered Structures ◽

Self Organized ◽

Carrier Transport Properties

ABSTRACTSelf-organized oligosilane thin films possess molecular orientation normal to substrates with multilayered structure. This unique order of σ-conjugated molecules results in good hole transport properties. In the present work, carrier transport properties at low temperature are studied for 1,10-diethyldecamethylsilane polycrystalline films. Even at a temperature as low as 173 K, a time-of-flight transient photocurrent waveform showed a clear plateau and a sharp decay, whose shape is similar to that at room temperature. Their hole mobility followed Arrhe-nius type temperature dependence with a small activation energy of 0.09 eV. The hole mobility of 6.3×10-5cm-2/Vs at 193 K was more than 2 orders of magnitude higher than that of typical polysilanes, which inevitably contain disordered structures hindering smooth carrier transport.

Download Full-text

Using ZnCo2O4 Nanoparticles as the Hole Transport Layer to Improve Long-Term Stability of Perovskite Solar Cells

10.21203/rs.3.rs-1145111/v1 ◽

2021 ◽

Author(s):

Bo-Rong Jheng ◽

Pei-Ting Chiu ◽

Sheng-Hsiung Yang ◽

Yung-Liang Tong

Keyword(s):

Solar Cells ◽

Metal Oxides ◽

Carrier Transport ◽

Perovskite Solar Cells ◽

Hole Transport ◽

Transport Layer ◽

Precipitation Method ◽

Hole Transport Layer ◽

Future Production

Abstract Inorganic metal oxides with the merits of high carrier transport capability, low cost and superior chemical stability have largely served as the hole transport layer (HTL) in perovskite solar cells (PSCs) in recent years. Among them, ternary metal oxides gradually attract attention because of the wide tenability of the two inequivalent cations in the lattice sites that offer interesting physicochemical perperties. In this work, ZnCo2O4 nanoparticles (NPs) were prepared by a chemical precipitation method and served as the HTL in inverted PSCs. The device based on the ZnCo2O4 NPs HTL showed better efficiency of 12.31% and negligible hysteresis compared with the one using PEDOT:PSS film as the HTL. Moreover, the device sustained 85% of its initial efficiency after 240 hours storage under a halogen lamps matrix exposure with an illumination intensity of 1000 W/m2, providing a powerful strategy to design long-term stable PSCs for future production.

Download Full-text

Resolution improvement by interpolation of charge sharing event position in 350µm pitch pixelated CdZnTe detectors

2011 IEEE Nuclear Science Symposium Conference Record ◽

10.1109/nssmic.2011.6152587 ◽

2011 ◽

Author(s):

Yongzhi Yin ◽

Ximeng Chen ◽

Heyu Wu ◽

Sergey Komarov ◽

Kuen Lee ◽

...

Keyword(s):

Charge Sharing ◽

Resolution Improvement ◽

Cdznte Detectors

Download Full-text

Investigation of Inverted Perovskite Solar Cells for Viscosity of PEDOT:PSS Solution

Crystals ◽

10.3390/cryst8090358 ◽

2018 ◽

Vol 8 (9) ◽

pp. 358 ◽

Cited By ~ 3

Author(s):

Pao-Hsun Huang ◽

Yeong-Her Wang ◽

Chien-Wu Huang ◽

Wen-Ray Chen ◽

Chien-Jung Huang

Keyword(s):

Thin Film ◽

Solar Cells ◽

Carrier Transport ◽

Perovskite Solar Cells ◽

Open Circuit ◽

Hole Transport ◽

Transport Layer ◽

Hole Transport Layer ◽

Considerable Impact ◽

Stable Performance

In this paper, we demonstrate that the inverted CH3NH3PbI3 (perovskite) solar cells (PSCs) based on fullerene (C60) as an acceptor is fabricated by applying an improved poly(3,4-ethlyenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution as a hole transport layer (HTL). The power conversion efficiency (PCE) of inverted PSCs is increased by 37.5% with stable values of open-circuit voltage (VOC) and fill factor (FF) because we enhance the viscosity of the PEDOT:PSS solution, indicating the perfect effect on both external quantum efficiency (EQE) and surface grain size. The characteristics of the PEDOT:PSS solution, which is being improved through facile methods of obtaining excellent growth of PEDOT:PSS thin film, have a considerable impact on carrier transport. A series of further processing fabrications, including reliable and feasible heating and stirring techniques before the formation of the PEDOT:PSS thin film via spin-coating, not only evaporate the excess moisture but also obviously increase the conductivity. The raised collection of holes become the reason for the enhanced PCE of 3.0%—therefore, the stable performance of FF and VOC are attributed to lower series resistance of devices and the high-quality film crystallization of perovskite and organic acceptors, respectively.

Download Full-text