Hydrazine-Free Precursor for Solution-Processed All-Inorganic Se and Se1-xTex Photovoltaics

TL;DR

This paper introduces a safer, hydrazine-free solution process for fabricating inorganic selenium-tellurium photovoltaic materials, achieving competitive efficiencies and excellent stability, advancing low-cost, environmentally friendly solar technology.

Contribution

It develops a hydrazine-free precursor system for solution-processed Se and Se1-xTex films, enabling efficient and stable photovoltaic devices with tunable bandgaps.

Findings

Achieved up to 2.73% efficiency in Se PVs

Demonstrated stable Se devices with no degradation after 1 month

Produced tunable bandgap films from 1.20 eV to 1.86 eV

Abstract

Selenium (Se) has reemerged as a promising absorber material for indoor and tandem photovoltaics (PVs), and its alloys with Te (Se1-xTex) offer a widely tunable bandgap. Solution processing of this materials system offers a route to low-cost fabrication. However, solution processing of Se has, thus far, only used hydrazine, which is an extremely hazardous solvent. In this work, we prepare and isolate propylammonium poly-Se and poly-Se-Te precursors from a safer thiol-amine solvent system. We formulate molecular inks by dissolving the precursor n,n-dimethylformamide (DMF) with a monoethanolamine (EA) additive and process high-quality Se and Se1-xTex films with bandgaps ranging from 1.20 eV to 1.86 eV. We fabricate PVs from these films using TiO2 and MoO3 charge transport layers (CTLs) to achieve power conversion efficiencies as high as 2.73% for Se and 2.33% for Se0.7Te0.3 under solar simulation. Se devices show excellent stability with no degradation after 1 month in air, enabled by the excellent stability of Se and the use of inorganic CTLs. This work represents an important step towards low-cost solution-phase processing of Se and Se1-xTex alloys for PVs and photodetectors with low toxicity and high bandgap tunability.