Numerical simulation of quantum dots as a buffer layer in CIGS solar cells: a comparative study

Abstract

Quantum bandgap buffer layers can improve sunlight absorption in the short wavelength region, hence improving the performance of CIGS solar cells. In this study, we use numerical modelling to determine the impact of various buffer layers' electrical characteristics on the performance of CIGS thin film photovoltaic devices, particularly, carrier concentration and the quantum effect. As well Ag2S buffer layer has been experimentally examined to fulfilment its effect in term of bulk and quantum bandgap. Experimental results depicted that, Ag2S QDs has polycrystalline nature of films, with smooth surface roughness, and average diameter 4 nm. Meanwhile, a simulation revealed that the Fermi level of the (n-buffer layer) material shifts closer to the conduction band with an increase in carrier concentration. The findings indicate that, a buffer layer with a wider bandgap and carrier concentration is an essential demand for achieving a device with a higher conversion efficiency and a broader bandgap-CBO window. It was attributed to beneficial synergistic effects of high carrier concentration and narrower depletion region, which enable carriers to overcome high CBO barrier. Most importantly, modelling results indicate that the optic-electrical characteristics of the buffer layer are critical in determining the progress of a CIGS solar cell.

An in-depth analysis of nucleation and growth mechanism of CdS thin film synthesized by chemical bath deposition (CBD) technique

“…Thus, this technique allowed better sub-monolayer coverage with a minimum particle aggregation. This helped in accurately controlling the size and spectral absorption properties of these QDs 3 . Some earlier reports showed that the semiconductor molecules such as CdS was a prospective buffer layer that could be employed as typical n-type heterojunction partners in current and upcoming thin-film PV devices due to its direct bandgap transition (Eg 2.4 eV), transparency, n-type conductivity, and a direct bandgap transition high electron affinity (4.2 eV) 4 .…”

Mechanism and principle of doping: realizing of silver incorporation in CdS thin filmviadoping concentration effect

“… 2 CdS is the most commonly implemented n-type buffer layer for thin-film solar cells with excellent performance. 3 As a buffer layer, for optimum minority carrier transport, CdS ought to be as thin as possible to ensure low series resistance, as a thicker film might reduce the Schottky barrier's effectiveness. Consequently to enhance the CdS conductivity, a specific process called doping is achieved by introducing impurities into the semiconductor crystal intentionally, which can be either acceptor or donor atoms in their crystalline lattice.…”

Investigating the Effect of Nonideal Conditions on the Performance of a Planar Sb2Se3-Based Solar Cell through SCAPS-1D Simulation

“…The doping concentration, also known as N D , is a crucial factor that affects the device performance . Nevertheless, in our particular instance, it seems that the variable is less.…”