Photoabsorption and Stability in Triple-Cation Perovskites Influenced by Interfacial Engineering of the Collector

Charge-carrier dynamics in three-dimensional perovskites is critical to understand for enhancing device performance because the photoabsorption mechanism in perovskites influences key functional devices such as photodetectors and solar cells. Temperature-dependent optoelectronic transport measurements were conducted on our triple-cation formulation for the first time from 4 to 300 K to investigate the role of an interfacial Ti underlayer, beneath the conventional Au collector electrode. The photocurrent was 10 times larger with the use of a Ti interfacial layer compared to only Au, where device measurements were made using a broadband white-light source at room temperature. As the temperature increased from 4 K, the photocurrent increased in both cases, consistent with the semiconducting nature of the triple-cation absorber. Besides computing the responsivity as a function of the power and temperature, time-domain measurements with ON/OFF pulses of incident white light showed the switching time constants to be in the tens to a few hundred milliseconds range and largely temperature-invariant for the two contacts examined. Finally, we constructed solar cells with the same triple-cation absorber in an n–i–p architecture with a spiro-OMeTAD hole-transport layer, but the collector was composed of both types of contacts. Exposing our devices to moisture-rich conditions of up to 70% relative humidity showed the Au/Ti-contacted devices to be more robust. Our experimental results demonstrate that the addition of a Ti interlayer improves the collector efficiency through the photoabsorption process while also potentially stabilizing the solar cells, compared to the bare Au, in moisture-rich environments.