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Title: An experimentally supported model for the origin of charge transport barrier in Zn(O,S)/CIGSSe solar cells

Zinc oxysulfide buffer layers with [O]:[S] of 1:0, 6:1, 4:1, 2:1, and 1:1 ratios were deposited by atomic layer deposition on Cu(In,Ga)(S,Se){sub 2} absorbers and made into finished solar cells. We demonstrate using Time-Resolved Photoluminescence that the minority carrier lifetime of Zn(O,S) buffered solar cells is dependent on the sulfur content of the buffer layer. τ{sub 1} for devices with [O]:[S] of 1:0–4:1 are <10 ns, indicating efficient charge separation in devices with low sulfur content. An additional τ{sub 2} is observed for relaxed devices with [O]:[S] of 2:1 and both relaxed and light soaked devices with [O]:[S] of 1:1. Corroborated with one-dimensional electronic band structure simulation results, we attribute this additional decay lifetime to radiative recombination in the absorber due to excessive acceptor-type defects in sulfur-rich Zn(O,S) buffer layer that causes a buildup in interface-barrier for charge transport. A light soaking step shortens the carrier lifetime for the moderately sulfur-rich 2:1 device when excess acceptors are passivated in the buffer, reducing the crossover in the dark and illuminated I-V curves. However, when a high concentration of excess acceptors exist in the buffer and cannot be passivated by light soaking, as with the sulfur-rich 1:1 device, then cell efficiency of themore » device will remain low.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [5] ; ;  [6] ; ;  [1] ;  [2]
  1. Energy Research Institute @ NTU - ERI@N, Interdisciplinary Graduate School, Nanyang Technological University, Singapore 639798 (Singapore)
  2. (Singapore)
  3. (SEA) Pte Ltd, 11 Bishan St. 21, Singapore 573943 (Singapore)
  4. Hochschule Ulm, Albert-Einstein-Allee 55, 89081 Ulm (Germany)
  5. Robert Bosch (SEA) Pte Ltd, 11 Bishan St. 21, Singapore 573943 (Singapore)
  6. Bosch Solar CISTech GmbH, Münstersche Str. 24, 14772 Brandenburg an der Havel (Germany)
Publication Date:
OSTI Identifier:
22489377
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 108; Journal Issue: 4; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BUFFERS; CARRIER LIFETIME; CHARGE TRANSPORT; LAYERS; PHOTOLUMINESCENCE; SIMULATION; SOLAR CELLS; SULFUR; SULFUR CONTENT; TIME RESOLUTION; VISIBLE RADIATION