Photovoltaic & Optoelectronic Device Group

Abstract:

Demand for energy in the context of climate change is driving rapid deployment of low-cost renewable energy and is accelerating efforts to deliver advanced photovoltaic (PV) technologies. In the past decade, the steeply rising solar-to-electrical power conversion efficiency of metal-halide perovskite solar cells (PSCs) make them a compelling candidate for next-generation PVs, with interesting applications envisaged beyond traditional solar plants. These include building integrated PVs, flexible solar-powered electronics, and solar vehicles and aircraft. Metal-halide perovskites benefit from the low formation energy for crystallization, a consequence of their ionic nature, which enables close to ambient-temperature solution or vapor-phase deposition and a thin-film crystallization process. However, the ease by which rapid crystallization occurs also introduces defects and local heterogeneities throughout the perovskite films and at internal interfaces, which limits their efficiency (1).

Abstract:

The efficiency and longevity of metal-halide perovskite solar cells are typically dictated by nonradiative defect-mediated charge recombination. In this work, we demonstrate a vapor-based amino-silane passivation that reduces photovoltage deficits to around 100 millivolts (>90% of the thermodynamic limit) in perovskite solar cells of bandgaps between 1.6 and 1.8 electron volts, which is crucial for tandem applications. A primary-, secondary-, or tertiary-amino–silane alone negatively or barely affected perovskite crystallinity and charge transport, but amino-silanes that incorporate primary and secondary amines yield up to a 60-fold increase in photoluminescence quantum yield and preserve long-range conduction. Amino-silane–treated devices retained 95% power conversion efficiency for more than 1500 hours under full-spectrum sunlight at 85°C and open-circuit conditions in ambient air with a relative humidity of 50 to 60%.