Low-Temperature and Solution-Processed Amorphous WO_<i>X</i> as Electron-Selective Layer for Perovskite Solar Cells

TLDR

The electron‑selective layer (ESL) is essential for collecting photogenerated electrons in perovskite solar cells, and low‑temperature preparation of ESLs is crucial for flexible device fabrication. This study aims to prepare a low‑temperature, solution‑processed amorphous WO(x) thin film to serve as an ESL in perovskite solar cells. The amorphous WO(x) film is fabricated by a facile solution‑processing route at low temperature and incorporated as the ESL in the device stack. The WO(x) ESL exhibits nanocave‑rich morphology, comparable light transmittance but higher conductivity than TiO₂, delivers comparable efficiency with higher short‑circuit current and lower open‑circuit voltage due to charge recombination, and overall proves to be an excellent ESL candidate.

Abstract

The electron-selective layer (ESL) is an indispensable component of perovskite solar cells (PSCs) and is responsible for the collection of photogenerated electrons. Preparing ESL at a low temperature is significant for future fabrication of flexible PSCs. In this work, solution-processed amorphous WO(x) thin film was prepared facilely at low temperature and used as ESL in PSCs. Results indicated that a large quantity of nanocaves were observed in the WO(x) thin film. In comparison with the conventional TiO2 ESL, the WO(x) ESL exhibited comparable light transmittance but higher electrical conductivity. Compared with the TiO2-based PSCs, PSCs that use WO(x) ESL exhibited comparable photoelectric conversion efficiency, larger short-circuit current density, but lower open-circuit voltage. Electrochemical characterization indicated that the unsatisfied open-circuit voltage and fill factor were caused by the inherent charge recombination. This study demonstrated that this material is an excellent candidate for ESL.