Unprecedented Wavelength Dependence of an Antimony Chalcohalide Photovoltaic Device

Abstract The output of a photovoltaic (PV) device follows the Shockley diode equation, where its open‐circuit voltage ( V OC ) is marginally modulated by the photocurrent density and light intensity. Herein, an unprecedented wavelength‐dependent photovoltaic effect (WDPE) in antimony chalcoiodide (SbSI) and SbSI:Sb 2 S 3 devices is reported, which demonstrate a rapid, reversible change of V OC by changing irradiation wavelength. The V OC in a SbSI:Sb 2 S 3 device is varied from 0.35 to 0.47 V under 375 and 515 nm light without a change of photocurrent. Such a dramatic shift in V OC is not observed in silicon, perovskites, or organic solar cells. WDPE allows for a wavelength‐recognizable single‐junction photodetector without using a color filter, and is not explained by the conventional diode model. Based on the time‐resolved evaluations of charge carriers, the interfacial metastable trap of a hot carrier generated by short‐wavelength light as the origin of the observed anomalous behavior is identified. Interestingly, the trap states and photocurrent kinetics are affected by humidity and ammonium gas, which provide another multifunctional aspect of the WDPE. These findings provide deep insight into PV physics and a new way to detect color using a single cell.