Performance and limits of 2.0 eV bandgap CuInGaS₂ solar absorber integrated with CdS buffer on F:SnO₂ substrate for multijunction photovoltaic and photoelectrochemical water splitting devices

Abstract

We report on the electrical properties of 2.0 eV bandgap (EG) CuInGaS2 (CIGS) solar absorbers integrated on SnO2:F (FTO) substrates and interfaced with CdS buffer layers for multijunction solar cells...

Conduction Band Cliff at the CdS/CuIn0.1Ga0.9Se2 Thin-Film Solar Cell Interface

“…We calculate an average shift of −0.04 ± 0.05 eV for the absorber core levels and −0.08 ± 0.07 eV for buffer-related core levels. The negligible additional shift of the absorber-related core levels might indicate that the Fermi level is pinned, suggesting a high defect concentration at the interface . This is typically accompanied by increased interface recombination and a drop in the open-circuit voltage V OC . ,, The presence of defects at the interface is corroborated by the observation of a significant valence-band tail in the CdS UPS spectrum, which suggests that such interfacial defects can lead to a poorer buffer layer growth with an increased number of defects in the CdS buffer layer itself.…”

“…The negligible additional shift of the absorber-related core levels might indicate that the Fermi level is pinned, suggesting a high defect concentration at the interface. 69 This is typically accompanied by increased interface recombination and a drop in the open-circuit voltage V OC . 40,43,69 The presence of defects at the interface is corroborated by the observation of a significant valence-band tail in the CdS UPS spectrum, which suggests that such interfacial defects can lead to a poorer buffer layer growth with an increased number of defects in the CdS buffer layer itself.…”

Comparing the net-energy balance of standalone photovoltaic-coupled electrolysis and photoelectrochemical hydrogen production

“…Si-based and III–V semiconductor based photocatalysts embedded in protection layers have shown high efficiency but may suffer from short operating lifetimes and high cost. 132 As examples, recent publications investigating the stability of GaAs in acidic or alkaline electrolyte 133 and the energetic limits to 2.0 eV bandgap CuInGaS 2 (CIGS) absorbers that could be embedded in PEC devices 134 may help to guide research in improving earth-abundant light absorbing materials. If high-efficiency PEC devices are developed, potentially with small amounts of precious metal co-catalysts, the theoretical efficiency limits for PEC devices may be achieved which has been calculated to exceed optimised PV-coupled electrolysis.…”

Novel Chalcopyrites for Advanced Photoelectrochemical Water Splitting

“…CIGS, CGSSe) as the main bottleneck of our HPE devices. 8 In fact, our optical and electronic studies thus far show that widebandgap chalcopyrites containing gallium and/or sulfur exhibit poor optical transmission (compared to their In-and Se-containing relatives), resulting in tandem structures with sub-optimal photocurrent densities. This could be due in part to Ga-related defects well-known in the PV community.…”