Tailoring Photoelectrochemical Performance and Stability of Cu(In,Ga)Se₂ Photocathode via TiO₂-Coupled Buffer Layers

Abstract

We report on the photoelectrochemical (PEC) performance and stability of Cu(In,Ga)Se (CIGS)-based photocathodes for photocatalytic hydrogen evolution from water. Various functional overlayers, such as CdS, TiO, ZnSnO, and a combination of the aforementioned, were applied on the CIGS to improve the performance and stability. We identified that the insertion of TiO overlayer on p-CIGS/n-buffer layers significantly improves the PEC performance. A multilayered photocathode consisting of CIGS/CdS/TiO/Pt exhibited the best current-potential characteristics among the tested photocathodes, which demonstrates a power-saved efficiency of 2.63%. However, repeated linear sweep voltammetry resulted in degradation of performance. In this regard, we focused on the PEC durability issues through in-depth chemical characterization that revealed the degradation was attributed to atomic redistribution of elements constituting the photocathode, namely, in-diffusion of Pt catalysts, out-diffusion of elements from the CIGS, and removal of the metal-oxide layers; the best-performing CIGS/CdS/TiO/Pt photocathode retained its initial performance until the TiO overlayer was removed. It was also found that the durability of CIGS photocathodes with a TiO-coated metal-oxide buffer layer such as ZnSnO was better than those with a TiO-coated CdS, and the degradation mechanism was different, suggesting that the stability of a CIGS-based photocathode can be improved by careful design of the structure.

Photoelectrocatalytic Materials for Solar Water Splitting

“…Nam and Shin have concluded that the performance degradation of CuInGaSe 2 based photocathode was caused by the atomic redistribution of elements constituting the electrode. The TiO 2 ‐coated Zn x Sn y O z buffer layer performed better than TiO 2 ‐coated CdS in suppressing the degradation . These discussions suggest that the PEC performance and stability of photoelectrodes fabricated with PV‐grade semiconductor can be improved through careful design of their configuration.…”

Photoelectrochemical water splitting: a road from stable metal oxides to protected thin film solar cells

“…Doing so on exible substrates can reduce device cost by enabling roll-to-roll fabrication and thus, facilitating technology implementation. 333 CIGS-CdS buried junctions have been adapted for water splitting 321,[334][335][336][337] (also on exible substrates 241 ), together with their earth-abundant equivalent CZTS. 240,335,[338][339][340][341] In 2 S 3 (ref.…”

Drop‐casted Platinum Nanocube Catalysts for Hydrogen Evolution Reaction with Ultrahigh Mass Activity

“…An electrocatalyst is a critical component of a PEC system and it is often bound on the surface of a light‐absorbing photoelectrode [2] . In the typical monolithic photoelectrode configuration, electrocatalysts are placed on the side where light is incident [3–5] . Therefore, not only catalytic activity but also light transmittance is an important factor to consider when designing an electrocatalyst‐coated photoelectrode system.…”

“…However, none has so far surpassed the catalytic activity of Pt. An obvious alternative approach is reducing the use of Pt, that is, improving the mass activity of Pt by forming a nanostructure with a high surface‐to‐volume ratio, such as nanoparticles, [5] nanowires, [20] patterned islands, [21] an atomic monolayer, [22] or even a collection of single atoms [23–25] . However, the past studies on forming nanostructured Pt encountered some issues such as inferior performance [26] and complex and/or harsh processing conditions [22] for the catalyst synthesis.…”