Effect of the ZnSnO/AZO Interface on the Charge Extraction in Cd-Free Kesterite Solar Cells

Abstract

Cu2ZnSnS4 (CZTS) is a promising absorber material to produce thin film solar cells thanks to its high absorption coefficient, low cost and low toxicity. CdS is commonly used as a buffer layer for CZTS solar cells but, beyond its toxicity, it has a nonoptimal band alignment with CZTS. ZnxSn1−xO (ZTO), based on earth-abundant and nontoxic elements and with a large and tunable band gap, is a suitable alternative buffer layer. In this paper, the atomic layer deposition (ALD) of ZTO was employed by testing different compositions and thicknesses. ALD not only leads to very compact and homogenous ZTO layers (enabling tuning the stoichiometry of the ZTO so prepared) but also makes the i-ZnO layer (usually sandwiched between the buffer layer and the transparent contact) redundant and detrimental. Through SCAPS simulation and impedance measurements, the ZnSnO/AZO interface impact on the Cd-free kesterite solar cells’ performances has been investigated, highlighting its leading role in achieving an effective charge extraction and the detrimental effect of the i-ZnO layer. With this approach, a solar cell based on an architecture simpler and more eco-friendly than the conventional one has been produced with comparable efficiencies.

Numerical Simulation of Highly Efficient Cs2TiI6 based Pb Free Perovskites Solar Cell with the Help of Optimized ETL and HTL Using SCAPS-1D Software

“…A flawless FF is impossible to accomplish. Even if we are able to get a zero series resistance (Rs) and an endlessly huge shunt resistance (Rsh), this is due to the solar cell's problematic diode behavior [34]. The effect of RS on photovoltaic parameters like VOC, JSC, FF, and power conversion efficiency was evaluated using the SCAPS-1D simulator.…”