Nonradiative and Radiative Recombination in CdS Polycrystalline Structures

Properties of polycrystalline CdS layers, employed in formation of the CdS-Cu2S heterostructures, have been studied by combining contactless techniques of the time and spectrally resolved photoluminescence (TR-PL) spectroscopy and microwave-probed photoconductivity (MW-PC) transients. The confocal microscopy has been employed to correlate the homogeneity of photoluminescence and grain size in CdS layers. Three types of samples with crystallite grain size of <1 μm (the I-type) and of 2–10 μm of homogeneous (II-type) and inhomogeneous (III-type) grain distribution have been separated. The simultaneous record of MW-PC and TR-PL responses ensures the same sampling area on the layer under investigation, as both (MW-PC and TR-PL) signals are generated by the same UV laser excitation beam. Two PL bands peaked at 500 and 700 nm were revealed. It has been demonstrated that photoluminescence intensity strongly depends on the properties of the polycrystalline 15–26 μm thick CdS layers with equilibrium carrier density of about  cm−3, which serve as the substrates to form CdS-Cu2S junctions. The different carrier decay components were ascribed to different microareas with characteristic MW-PC and PL decay lifetimes of 2–10 ns, ascribed to microcrystallites with PL instantaneous decay lifetimes of 40–200 ns, and MW-PC decay lifetimes in the range of 100–1000 μs attributed to the inter-crystallite areas of CdS polycrystalline material.

[1]  Kuniaki Tanaka,et al.  Deposition of copper sulfide on the surface of poly(ethylene terephthalate) and poly(vinyl alcohol) films in aqueous solution to give electrically conductive films , 1993 .

[2]  Conductive copper sulfide thin films on polyimide foils , 2001 .

[3]  P. K. Nair,et al.  Copper selenide thin films by chemical bath deposition , 1999 .

[4]  J. C. Phillips,et al.  Stretched exponential relaxation in molecular and electronic glasses , 1996 .

[5]  Masakazu Aono,et al.  Structural studies of copper sulfide films: effect of ambient atmosphere , 2008, Science and technology of advanced materials.

[6]  Achim Müller,et al.  The formation of Cu2S from the elements: I. Copper used in form of powders , 2000 .

[7]  S. McGlynn,et al.  Concepts in Photoconductivity and Allied Problems. , 1964 .

[8]  I. Bratu,et al.  Spray pyrolysis deposition of CuS thin films , 1997 .

[9]  Jacques I. Pankove,et al.  Optical Processes in Semiconductors , 1971 .

[10]  E. Simoen,et al.  Excess carrier cross-sectional profiling technique for determination of the surface recombination velocity , 2001 .

[11]  S. Havlin,et al.  Diffusion in disordered media , 1991 .

[12]  J. M. Codina,et al.  Electrical properties of polycrystalline In-doped CdS thin films , 1984 .

[13]  B. Ray.  II-VI compounds , 1969 .

[14]  Tomas Ceponis,et al.  Spectroscopy of Deep Traps in Cu2S-CdS Junction Structures , 2012, Materials.

[15]  E. Gaubas,et al.  FLUENCE DEPENDENT VARIATIONS OF BARRIER CHARGING AND GENERATION CURRENTS IN NEUTRON AND PROTON IRRADIATED Si PARTICLE DETECTORS , 2011 .

[16]  Kevin Barraclough,et al.  I and i , 2001, BMJ : British Medical Journal.

[17]  E. Gaubas,et al.  Impact of generation current on the evaluation of the depletion width in heavily irradiated Si detectors , 2011 .

[18]  J. C. Phillips,et al.  Microscopic aspects of Stretched Exponential Relaxation (SER) in homogeneous molecular and network glasses and polymers , 2010, 1005.0648.

[19]  G. Tamulaitis,et al.  Barrier capacitance characteristics of CdS–Cu2S junction structures , 2013 .

[20]  M. Burgelman,et al.  Reactive sputtering of large-area Cu2S/CdS solar cells , 1986 .

[21]  Lorenzo Pavesi.  Influence of dispersive exciton motion on the recombination dynamics in porous silicon , 1996 .

[22]  S. Juršėnas,et al.  Carrier and defect dynamics in photoexcited semi-insulating epitaxial GaN layers , 2004 .

[23]  Guangwei She,et al.  Template-free electrochemical synthesis of single-crystal CuTe nanoribbons , 2008 .

[24]  Zhaodong Nan,et al.  Formation of various morphologies of copper sulfides by a solvothermal method , 2006 .

[25]  W. Marsden.  I and J , 2012 .

[26]  M. A. Korzhuev.  Dufour effect in superionic copper selenide , 1998 .

[27]  M. León,et al.  On the photoconductivity of copper sulphide polycrystalline thin films , 1985 .

[28]  S. Martinuzzi,et al.  CuxS/Cd1−yZnyS/CdS evaporated back-wall bifilm solar cell , 1982 .