Regimes of current transport mechanisms in CdS/CdTe solar cells

Bayhan, H, Dagkaldiran, ET, Major, JD ORCID: 0000-0002-5554-1985, Durose, K ORCID: 0000-0003-1183-3211 and Bayhan, M
(2019) Regimes of current transport mechanisms in CdS/CdTe solar cells. SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 34 (7). 075013-075013.

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Forward bias recombination (current transport) mechanisms have been evaluated for thin film solar cells and correlated to the in-gap trap levels present. Here CdTe/CdS devices were chosen as an archetypal example of a modern thin film solar cell, and a set of devices with a range of design variables was used in order to reveal the full range of behaviours that may operate to limit current transport. Experimental current-voltage-temperature datasets were compared to mathematical models of transport, and the in-gap traps were evaluated by thermal admittance spectroscopy. The current transport mechanisms operating are presented on a temperature-voltage diagram. Three regimes were identified: at 'intermediate' voltages, the behaviour was temperature dependent. From 300 K down to 240 K, thermally activated Shockley Read Hall recombination mediated by a 0.38 eV trap (V Cd) dominated the transport. Between 200 and 240 K the transport was thermally activated but below 200 K the mechanism became dominated by tunnel assisted interface recombination. At 'low' voltages (and for all devices at all voltages when measured at T < 200 K) band to band recombination is via multi-step tunnelling through in-gap states. At high voltage, the forward current is dominated by the well-known limiting effect of the back Schottky contact to the CdTe which is in reverse bias. The current transport behaviour is also correlated with the n-CdS thickness and CdCl2 processing conditions, both of which are critical to device performance.

Item Type: Article
Uncontrolled Keywords: CdS/CdTe solar cell, current transport mechanisms, admittance spectroscopy
Depositing User: Symplectic Admin
Date Deposited: 10 Dec 2019 08:54
Last Modified: 19 Jan 2023 00:18
DOI: 10.1088/1361-6641/ab23b5
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