New ways of developing glass/conducting glass/CdS/CdTe/metal thin-film solar cells based on a new model

Abstract

Making use of the authors' experimental results and the evidence available in the literature, an alternative model for glass/conducting glass/CdS/CdTe/metal solar cells has been formulated. This model explains the device behaviour in terms of a combination of a hetero-junction and a large Schottky barrier at the CdTe/metal interface. The main experimental observations available to date are described and compared with the currently assumed p-n junction model and this proposed new model. It is shown that the proposed model explains almost all the experimental results more satisfactorily. The paper describes the guidelines to further increase the performance efficiencies based on the new model. Following these new guidelines, the authors have fabricated improved devices producing open circuit voltage (V oc ) values over 600 mV, fill factor (FF) values over 0.60 and the short-circuit current density (J sc ) values over 60 mA cm −2 for best devices. Although the V oc and FF could be further improved, the remarkable improvement of J sc indicates the possibility of further development of multilayer graded band gap tandem solar cells based on CdS/CdTe system.

Unravelling complex nature of CdS/CdTe based thin film solar cells

“…This was first published in 2002, and the relevant energy band diagram is shown in Fig. 8b [7]. Clearly the two device concepts produced another controversy in the solid state physics area of this device.…”

“…Clearly the two device concepts produced another controversy in the solid state physics area of this device. Many experimental results could be explained by both device structures, but the second device model satisfactorily explains almost all device characteristics [7]. This situation had created confusion in understanding and describing properties of CdS/ CdTe based PV device characteristics for a long period of time over three decades.…”

“…The photo-generated current components produced by these two rectifying interfaces (n-n and SB) add-up together, and therefore these two junctions are connected in parallel. Then, this is a tandem solar cell with two rectifying junctions [6,7] and capable of producing improved performance when compared to a simple p-n junction device. This was first published in 2002 [7], and it is now becoming clearer from the latest research [8].…”

“…Then, this is a tandem solar cell with two rectifying junctions [6,7] and capable of producing improved performance when compared to a simple p-n junction device. This was first published in 2002 [7], and it is now becoming clearer from the latest research [8]. All the existing and relevant knowledge from the literature and new experimental results are combined to present in this paper.…”

Analysis of electrodeposited CdTe thin films grown using cadmium chloride precursor for applications in solar cells

“…However, cathodic voltages closer to the intrinsic voltage (V i ) would be favourable for the fabrication of devices due to high crystallinity, better optical and morphological properties achieved in stoichiometric or near-stoichiometric CdTe layers. It should be noted that based on the understanding as published by Dharmadasa et al (2002) [21,30,31] and new results as published by independent researchers such as Reese et al (2015) [23] and Burst et al (2016) [22], fabricating devices with slightly Cd-rich CdTe is favourable due to increased carrier lifetime, defect reduction amongst other advantages.…”