Cpm Measurenents on a-Si:H Based Pin Solar Cells: Thickness and Bias Voltage Effects

1989 ◽  
Vol 149 ◽  
Author(s):  
H. Rübel ◽  
M. Gorn ◽  
B. Scheppat ◽  
R. Geyer ◽  
P. Lechner ◽  
...  
Keyword(s):  
Solar Cells ◽  
Valence Band ◽  
Bias Voltage ◽  
Dangling Bond ◽  
Defect Region ◽  
Pin Diodes ◽  
Voltage Bias ◽  
Band Tailing ◽  
Photocurrent Spectra

ABSTRACTWe use measurements of subbandgap photocurrent spectra on films, barrier structures and pin cells of different thicknesses to estimate the valence band tailing and to characterize the dangling bond defect region. Large differences in signal sizes in the structures are observed and particularly for thick and thin pin-diodes, the dependence of the signal on voltage bias is discussed. In pin-diodes, these effects can be explained by a change of defect occupation in the i-layer.

scholarly journals Calculation of Band Offsets of Mg(OH)2-Based Heterostructures

2021 ◽  
Vol 2 (3) ◽  
pp. 274-283
Author(s):  
Masaya Ichimura
Keyword(s):  
Solar Cells ◽  
Valence Band ◽  
Dye Sensitized Solar Cells ◽  
Band Alignment ◽  
First Principles Calculation ◽  
Band Edge ◽  
Level Energy ◽  
Type I ◽  
Valence Band Edge ◽  
Generalized Gradient

The band alignment of Mg(OH)2-based heterostructures is investigated based on first-principles calculation. (111)-MgO/(0001)-Mg(OH)2 and (0001)-wurtzite ZnO/(0001)-Mg(OH)2 heterostructures are considered. The O 2s level energy is obtained for each O atom in the heterostructure supercell, and the band edge energies are evaluated following the procedure of the core-level spectroscopy. The calculation is based on the generalized gradient approximation with the on-site Coulomb interaction parameter U considered for Zn. For MgO/Mg(OH)2, the band alignment is of type II, and the valence band edge of MgO is higher by 1.6 eV than that of Mg(OH)2. For ZnO/Mg(OH)2, the band alignment is of type I, and the valence band edge of ZnO is higher by 0.5 eV than that of Mg(OH)2. Assuming the transitivity rule, it is expected that Mg(OH)2 can be used for certain types of heterostructure solar cells and dye-sensitized solar cells to improve the performance.

Band Tailing and Transport in a-SiGe:H-Alloys

1989 ◽  
Vol 149 ◽  
Author(s):  
G. H. Bauer ◽  
C. E. Nebel ◽  
M. B. Schubert ◽  
G. Schumm
Keyword(s):  
Raman Scattering ◽  
Valence Band ◽  
State Density ◽  
Conduction Band Edge ◽  
Compound Structure ◽  
Tail State ◽  
Photocurrent Spectroscopy ◽  
Transport Studies ◽  
Small X ◽  
Band Tailing

ABSTRACTOptical and transport studies of both cb- and vb-tail states in a-Si1−xGex:H such as subband absorption (PDS), instationary photocurrent experiments (TOF, PTS) for electrons and holes, Modulated Photocurrent Spectroscopy (MPS), and Raman scattering have been performed. The main consequences of Ge-alloying into the a-Si:H network are i) an increase in cb-tail state density at the conduction band edge and in the exponential cb- tail even for small x (O<x<0.3), accompanied by ii) a rise in deep cb-tail and midgap states which to some extent can be reduced by appropriate deposition methods; iii) at the valence band side up to x≈0.3 the tail seems not to be affected at all and for 0.3<x<0.9 the vb-tail obviously can be kept similar to that of a-Si:H (Evo≈(50–60) meV). Halfwidths of Raman TO-like modes point to the existence of a rigid Si-network in O<x<0.3 in which Ge is incorporated and to a transition at x>0.35 into a Si-Ge compound structure with maximum disorder at x≈0.5.

Comparison of photocurrent spectra measured by FTPS and CPM for amorphous silicon layers and solar cells

2008 ◽  
Vol 354 (19-25) ◽  
pp. 2167-2170 ◽  
Author(s):  
J. Holovský ◽  
A. Poruba ◽  
A. Purkrt ◽  
Z. Remeš ◽  
M. Vaněček
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Photocurrent Spectra

scholarly journals An antibonding valence band maximum enables defect-tolerant and stable GeSe photovoltaics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shun-Chang Liu ◽  
Chen-Min Dai ◽  
Yimeng Min ◽  
Yi Hou ◽  
Andrew H. Proppe ◽  
...  
Keyword(s):  
Solar Cells ◽  
Valence Band ◽  
Surface Passivation ◽  
Defect Density ◽  
Perovskite Solar Cells ◽  
Valence Band Maximum ◽  
Ambient Conditions ◽  
Band Maximum ◽  
Point Tracking ◽  
Power Point

AbstractIn lead–halide perovskites, antibonding states at the valence band maximum (VBM)—the result of Pb 6s-I 5p coupling—enable defect-tolerant properties; however, questions surrounding stability, and a reliance on lead, remain challenges for perovskite solar cells. Here, we report that binary GeSe has a perovskite-like antibonding VBM arising from Ge 4s-Se 4p coupling; and that it exhibits similarly shallow bulk defects combined with high stability. We find that the deep defect density in bulk GeSe is ~1012 cm−3. We devise therefore a surface passivation strategy, and find that the resulting GeSe solar cells achieve a certified power conversion efficiency of 5.2%, 3.7 times higher than the best previously-reported GeSe photovoltaics. Unencapsulated devices show no efficiency loss after 12 months of storage in ambient conditions; 1100 hours under maximum power point tracking; a total ultraviolet irradiation dosage of 15 kWh m−2; and 60 thermal cycles from −40 to 85 °C.

Sensitization of the Holes Lifetime by the Addition of Dangling Bonds in a-Si:H

2001 ◽  
Vol 664 ◽  
Author(s):  
L.F. Fonseca ◽  
S. Z. Weisz ◽  
I. Balberg
Keyword(s):  
Valence Band ◽  
Important Implication ◽  
Dangling Bond ◽  
Dangling Bonds ◽  
Defect States ◽  
Band Tail ◽  
Present Understanding

ABSTRACTThis paper is concerned with the phenomenon of the increase of the holes lifetime with the increase of the dangling bond concentration in a-Si:H. This rather surprising phenomenon that was observed, but not discussed, previously is shown to be a non-trivial effect which is based on the charged nature of the dangling bonds and a special scenario of the concentrations of the various defect states in the material. The most important implication of our study is that the charged dangling bonds can sensitize the valence band tail states, in contrast with the accepted roles of these types of states. The present understanding suggests that many new interesting phototransport phenomena can be found in a-Si:H.

Infrared Electroabsorption Spectra in Amorphous Silicon Solar Cells

1999 ◽  
Vol 557 ◽  
Author(s):  
J. H. Lyou ◽  
Eric A. Schiff ◽  
Steven S. Hegedus ◽  
S. Guha ◽  
J. Yang
Keyword(s):  
Solar Cells ◽  
Infrared Spectrum ◽  
Amorphous Silicon ◽  
Optical Transition ◽  
Silicon Solar Cells ◽  
Reverse Bias Voltage ◽  
Dangling Bond ◽  
Applied Bias ◽  
Infrared Band ◽  
Peak Energy

AbstractWe report measurements of the infrared spectrum detected by modulating the reverse-bias voltage across amorphous silicon pin solar cells and Schottky barrier diodes. We find a band with a peak energy of 0.8 eV. The existence of this band has not, to our knowledge, been reported previously. The strength of the infrared band depends linearly upon applied bias, as opposed to the quadratic dependence for interband electroabsorption in amorphous silicon.The band's peak energy agrees fairly well with the known optical transition energies for dangling bond defects, but the linear dependence on bias and the magnitude of the signal are surprising if interpreted using an analogy to interband electroabsorption. A model based on absorption by defects near the n/i interface of the diodes accounts well for the infrared spectrum.

Chemical bath process for highly efficient Cd-free chalcopyrite thin-film-based solar cells

2000 ◽  
Vol 77 (9) ◽  
pp. 723-729
Author(s):  
A Ennaoui
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Solar Cells ◽  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Subsequent Development ◽  
Energy Band Diagram ◽  
Buffer Layers ◽  
Band Offsets ◽  
Good Surface

The highest efficiency for Cu(Ga,In)Se2 (CIGS) thin-film-based solar cells has been achieved with CdS buffer layers prepared by a solution growth method known as the chemical bath deposition (CBD). With the aim of developing Cd-free chalcopyrite-based thin-film solar cells, we describe the basic concepts involved in the CBD technique. The recipes developed in our laboratory for the heterogeneous deposition of good-quality thin films of ZnO, ZnSe, and MnS are presented. In view of device optimization, the initial formation of chemical-bath-deposited ZnSe thin films on Cu(Ga,In)(S,Se)2 (CIGSS) and the subsequent development of the ZnSe/CIGSS heterojunctions were investigated by X-ray photoelectron spectroscopy (XPS). The good surface coverage was controlled by measuring changes in the valence-band electronic structure as well as changes in the In4d, Zn3d core lines. From these measurements, the growth rate was found to be around 3.6 nm/min. The valence band and the conduction band-offsets ΔEV and ΔEC between the layers were determined to be 0.60 and 1.27 eV, respectively for the CIGSS/ZnSe interface. The energy-band diagram is discussed in connection with the band-offsets detemined from XPS data. A ZnSe thickness below 10 nm has been found to be optimum for achieving a homogeneous and compact buffer layer on CIGSS with a total area efficiency of 13.7%.PACS No.: 42.70

Control of Materials and Interfaces in μc-Si:H-based Solar Cells Grown at High Rate

2011 ◽  
Vol 1321 ◽  
Author(s):  
Yasushi Sobajima ◽  
Chitose Sada ◽  
Akihisa Matsuda ◽  
Hiroaki Okamoto
Keyword(s):  
Growth Rate ◽  
Solar Cells ◽  
Film Growth ◽  
Defect Density ◽  
Density Measurement ◽  
High Growth ◽  
High Growth Rate ◽  
High Rate ◽  
Bulk Region ◽  
Dangling Bond

ABSTRACTGrowth process of microcrystalline silicon (μc-Si:H) using plasma-enhanced chemicalvapor- deposition method under high-rate-growth condition has been studied for the control of optoelectronic properties in the resulting materials. We have found two important things for the spatial-defect distribution in the resulting μc-Si:H through a precise dangling-bond-density measurement, e. g., (1) dangling-bond defects are uniformly distributed in the bulk region of μc- Si:H films independent of their crystallite size and (2) large number of dangling bonds are located at the surface of μc-Si:H especially when the film is deposited at high growth rate. Starting procedure of film growth has been investigated as an important process to control the dangling-bond-defect density in the bulk region of resulting μc-Si:H through the change in the electron temperature by the presence of particulates produced at the starting period of the plasma. Deposition of Si-compress thin layer on μc-Si:H grown at high rate followed by thermal annealing has been proposed as an effective method to reduce the defect density at the surface of resulting μc-Si:H. Utilizing the starting-procedure-controlling method and the compress-layerdeposition method together with several interface-controlling methods, we have demonstrated the fabrication of high conversion-efficiency (9.27%) substrate-type (n-i-p) μc-Si:H solar cells whose intrinsic μc-Si:H layer is deposited at high growth rate of 2.3 nm/sec.

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