Nanoscale Performance Disorder Dictates Perovskite Solar Cell Performance and Stability

Metal halide perovskites are attractive candidates in optoelectronic devices such as solar cells and LEDs. However, unlike conventional materials such as silicon, perovskite thin films are polycrystalline with profound, microscopic disorder in structure, chemistry and optoelectronic quality^1–3. Furthermore, contact layers for charge extraction and their interfaces with the perovskite thin film are also highly disordered, causing large non-radiative recombination losses and current extraction losses⁴. The implications of the numerous forms of disorder for long term solar cell performance are still unclear.

In this presentation, we demonstrate the use of a multimodal microscopy toolkit to probe the interplay between structure, chemistry and optoelectronic performance on the nanoscale⁵. We employ hyperspectral and voltage-dependent luminescence microscopy to probe non-radiative voltage losses and charge extraction losses by extracting current-voltage (JV) curves at each spatial point. Combined with nanoprobe synchrotron X-ray microscopy on the same scan areas before and after extended operational stress testing, we unveil point by point changes to recombination and charge transport across length scales from device pixel to sub-micron.

We show that devices can tolerate substantial variations in local chemical composition, however any increase in disorder associated with charge extraction results in lower performance and stability. We find that compositional engineering is a robust and reliable way to reduce this charge extraction disorder. Passivation of the interfaces using surface treatments, results in the lowest disorder across the device space explored – however these treatments can be double edged swords as the interfaces often become the stability weak-link and reduce long term durability. Taken together, these operando measurements uniquely unveil the underpinnings of perovskite solar cell performance and stability.

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