Characterization of thin CdTe solar cells with a CdSeTe front layer
- PDF / 1,616,382 Bytes
- 10 Pages / 432 x 648 pts Page_size
- 66 Downloads / 186 Views
MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.332
Characterization of thin CdTe solar cells with a CdSeTe front layer Alexandra M. Bothwell, Jennifer A. Drayton, Pascal M. Jundt, and James R. Sites Colorado State University, Fort Collins, CO 80523, U.S.A.
ABSTRACT
Thin CdTe photovoltaic device efficiencies show significant improvement with the incorporation of a CdSeTe alloy layer deposited between a MgZnO emitter and CdTe absorber. CdTe and CdSeTe/CdTe devices fabricated by close-space sublimation with a total absorber thickness of 1.5 µm are studied using microscopy measurements and show minimal diffusion of Se into the CdTe. Current loss analysis shows that the CdSeTe layer is the primary absorber in the CdSeTe/CdTe structure, and fill factor loss analysis shows that ideality-factor reduction is the dominant mechanism of fill factor loss. Improvement in the CdSeTe/CdTe absorber quality compared to CdTe is also reflected in spectral and timeresolved photoluminescence measurements. Current density vs. voltage measurements show an increase in current density of up to 2 mA/cm² with the addition of CdSeTe due to a band gap shift from 1.5 to 1.42 eV for CdTe and CdSeTe/CdTe absorbers respectively. Voltage deficit is lower with the incorporation of the CdSeTe layer, corroborated by improved electroluminescence intensity. The addition of CdSeTe into CdTe device structures has increased device efficiencies from 14.7% to 15.6% for absorbers with a total thickness less than two microns.
INTRODUCTION Cadmium telluride (CdTe) is an advantageous absorber material for photovoltaic applications because its favourable absorption coefficient allows for an ultra-thin absorber layer, which reduces deposition time and fabrication costs [1]. CdTe photovoltaic devices have demonstrated immense improvement in the past decade with efficiencies reaching 18.6% and 22.1% for modules and research-based small area devices respectively [2, 3]. Rapid progress is due in part to developments in device architecture, such as the incorporation of a cadmium selenium telluride (CdSe 1-xTex) alloy into the absorber layer.
Downloaded from https://www.cambridge.org/core. Columbia University - Law Library, on 03 Sep 2019 at 10:59:37, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2019.332
A CdSeTe/CdTe bilayer absorber improves photovoltaic efficiency compared to a single CdTe absorber by increasing the short-circuit current density (JSC) of the device. Due to a 100-meV narrower bandgap than CdTe, the CdSeTe layer increases photon absorption above the conduction band, thus improving current collection [4]. Se also passivates bulk defects in the absorber, leading to increased device performance [5]. Previous work has shown successful incorporation of CdSeTe and good performance using a CdSeTe/CdTe bilayer, however, only for absorbers greater than 4.0 µm with CdSeTe purposefully diffused into the CdTe layer [4]. This study demonstrates that a 1.5 μm Cd
Data Loading...
