where I0 is the incident intensity per pulse, e is the elementary charge, β is the ratio between the inner broad and narrow dimensions of the waveguide, FA is the fraction of incident photons absorbed within the sample, φ is the charge carrier generation yield, and Σμ is the sum of electron and hole mobilities Neutral density filters were selected to adjust the light intensity in the range of Photoluminescence spectroscopy: Low temperature photoluminescence measurements were carried out in a home-built system equipped with a helium flow cryostat under 663-nm wavelength diode laser excitation source. The emitted luminescence was collected through off-axis positioned parabolic mirrors and focused into a fiber, and spectrally resolved by a monochromator and subsequently detected by a Si-charge-coupled device (CCD) and an InGaAs diode array. All the data were corrected with a calibration lamp with a known spectrum. Neutral density filters were used to vary the power for excitation intensity dependent PL. Dual-working electrode (DWE) fabrication: For DWE measurements, the Sb2Se3 was synthesized as described above. The main difference when compared to the conventional single working electrode setup is that a second working electrode (WE2, which measures the surface potential) is fabricated on the catalyst (Pt), which enables the determination of the photovoltage (the difference between the back contact potential (WE1) and the front contact potential (WE2)).