# Facile Green Synthesis of N-Type InP Thin-Film Photoanodes with Enhanced Photoelectrochemical Performance for Solar Hydrogen Generation

## TL;DR

This paper presents a simple and eco-friendly method to create efficient InP thin films for solar hydrogen production.

## Contribution

A green synthesis method for n-type InP thin-film photoanodes with enhanced performance is introduced.

## Key findings

- InP thin films were synthesized using a doctor blade coating method with NaH2PO2 as a phosphorus source.
- The films achieved a photocurrent density of 1.8 mA·cm−2 under AM 1.5 illumination.
- The method enables scalable and sustainable production of III–V semiconductors for solar hydrogen generation.

## Abstract

Indium phosphide (InP) is a promising photoactive material for solar-driven hydrogen production owing to its optimal bandgap, high carrier mobility, and broad solar absorption. However, conventional InP fabrication relies on costly wafers and toxic precursors, limiting its scalability and sustainability. Here, we demonstrate a simple and environmentally friendly route to synthesize n-type InP thin-film photoanodes by phosphidating indium films prepared via doctor blade coating on ITO substrates, using NaH2PO2 as a phosphorus source. Structural and spectroscopic analyses (XRD, Raman, XPS, PL) confirmed the successful formation of crystalline InP with optimum quality at 425 °C. Photoelectrochemical measurements revealed a significant photocurrent density of 1.8 mA·cm−2 under AM 1.5 illumination, with extended photoresponse into the near-infrared region. Mott–Schottky and EIS analyses indicated efficient charge separation, low transfer resistance, and unintentional n-type doping due to Sn diffusion from the ITO substrate. This facile and green synthesis route not only provides a scalable approach to III–V semiconductors but also highlights InP thin films as cost-effective and efficient photoanodes for sustainable solar hydrogen generation.