Codesigning Alloy Compositions of CdSe_yTe_1−y Absorbers and Mg_xZn_1−xO Contacts to Increase Solar Cell Efficiency

Abstract

Thin‐film solar cells such as CdTe are a major commercial photovoltaic technology, with more than 25 GW installed worldwide and levelized costs of electricity competitive with fossil fuels. Further progress may result from integrating CdSeyTe1−y absorbers with MgxZn1−xO contacts, but the device efficiency is difficult to maximize due to coupled dependence on chemical composition of both alloys. Herein, a high‐throughput approach is demonstrated to codesign chemical compositions in alloyed MgxZn1−xO/CdSeyTe1−y thin‐film solar cells, using combinatorial libraries of PV devices with orthogonal composition gradients in CdSeyTe1−y absorbers and MgxZn1−xO contacts. It is found that the solar cell performance is a strong and coupled function of both elemental compositions, with efficiency up to 17.7% (VOC = 836 mV, fill factor = 69%, JSC = 30.6 mA cm−2) at atomic compositions of Mg/(Mg + Zn) ≈18% and average Se/(Se + Te) ≈4%. These performance trends among >100 devices are explained by >100 ns lifetime of photoexcited charge carriers at the MgxZn1−xO/CdSeyTe1−y interface where strong Se accumulation is also observed. This study reports the optimal compositions of the commercially relevant MgxZn1−xO/CdSeyTe1−y solar cells and demonstrates a general approach to codesigning performance of alloyed thin‐film solar cells and other optoelectronic devices.

Concurrent Design of Alloy Compositions of CZTSSe and CdZnS Using SCAPS Simulation: Potential Routes to Overcoming VOC Deficit

“…Finally, the co-design of the elemental compositions of the electron transport layer (ETL) and the absorber represents a new field, and its widespread application across various materials has not been widely explored. One of these few efforts was devoted to the codesign of alloy compositions of CdSe x Te 1_x (as an absorber material) and Mg y Zn 1-y O (as an ETL) [49]. In their experimental study, the authors revealed that the solar cell performance is a strongly coupled function of both x and y compositions.…”

“…In their experimental study, the authors revealed that the solar cell performance is a strongly coupled function of both x and y compositions. They achieved a PCE of up to 17.7% at specific atomic compositions (x = 0.04 and y = 0.18) [49]. As this field of research is advancing, a need for simulation studies is mandatory to investigate and evaluate new material systems and to provide design guidelines for the corresponding solar cells.…”