Publication date: 11th March 2026
Defective electronic states in semiconductors significantly influence the efficiency of photovoltaic devices. In particular, deep sub-bandgap defects induce nonradiative recombination of charge carriers, ultimately resulting in a loss of solar cell open-circuit voltage. Understanding the nature of such defects is essential for boosting solar cell efficiency.
Most sensitive characterization techniques used to study defect response and behavior in perovskite solar cells require complete device stacks. This makes it difficult to distinguish between the contributions of the perovskite layer or other adjacent layers [1]. Studying how the intrinsic perovskite defect response alters when passivating or charge-transport layers are deposited atop without the fabrication of a complete solar cell device allows for a more direct analysis of the defect response.
Here, we demonstrate that sensitive photoconductivity (PC) spectroscopy on lateral photoresistor devices enables direct detection of sub-bandgap defect states in metal-halide perovskites without requiring a full solar cell stack. By combining PC with sensitive photoluminescence measurements, we demonstrate that perovskites contain radiative deep electron traps that can be optically populated via sub-bandgap excitation, leaving long-lived holes that contribute to the PC signal [2]. Surface treatments strongly influence the observed signal, with choline chloride passivation reducing surface defect density, while fullerene-based electron-transport layers can extract trapped electrons and change the trap occupancy. Experiments using inverted photoresistor geometries reveal that PC spectroscopy is surface-sensitive, making it a powerful method to study interface treatments that would be difficult to disentangle using conventional photocurrent spectroscopy on complete devices. This paves the way for characterizing perovskite materials and studying how surface treatments affect defect density and distribution.
The authors acknowledge funding from the Dutch Research Council (NWO) (Spinoza grant) and the European Research Council (Grant Agreement No. 101098168).
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