National Renewable Energy Laboratory (NREL)

A few months ago, researchers from the University of Alabama, Jackson State University and NREL reported high-performance perovskite solar cells (PSCs) fabricated using rapid photonic annealing (RPA) based on ultraviolet light-emitting diode (UV-LED) sources. 

The schematic of thermal annealing (TA) and rapid photon annealing (RPA) annealing of SnO₂ ETL and perovskite absorber. Image from: Small

This approach replaces conventional thermal annealing with a fast, energy-efficient, and layer-specific process that enables precise control of film crystallization within seconds. The resulting PSCs achieved a power conversion efficiency of 23.03% - the highest reported for optically annealed perovskite devices.

Perovskite solar cells (PSCs) tend to degrade rapidly under reverse bias, a condition that arises during partial shading. At voltages below −2 V, current forced backward through shaded cells produces localized hotspots and thermal runaway, leading to catastrophic breakdown. Unlike silicon solar cells, where bypass diodes mitigate reverse bias, PSCs remain highly vulnerable due to structural weaknesses in their active layers, making it essential to pinpoint the mechanisms driving this failure.

Image credit: Joule

A recent study, led by the McGehee group at the University of Colorado Boulder in collaboration with the National Renewable Energy Laboratory (NREL), identifies nanoscale to microscale defects - particularly pinholes in the perovskite film - as the principal trigger of breakdown events. These defects are introduced during the solution-processing fabrication method, which is prone to creating gaps and thin spots due to film inhomogeneity. Although such pinholes have only a minor impact on overall power conversion efficiency, they represent weak points where localized heating and failure originate under stress conditions.

Perovskite solar cells (PSCs) are reaching impressive power conversion efficiencies, but long-term durability remains a major barrier to real-world impact. In a recent Perspective article, NREL researchers highlight why current stress tests (light, heat, humidity, etc.) are insufficient: they don’t accurately predict how PSCs will perform under field conditions. 

A more realistic path forward is a durability learning cycle, where lab and field testing continuously inform each other. The NREL team is recommending investigating the durability of perovskite solar modules - starting by placing them outside.

Halide perovskite solar cells with mixed-cation compositions often face instabilities under continuous illumination due to the deprotonation of methylammonium (CH₃NH₃⁺, MA⁺) cations. To address this issue, researchers from Tsinghua University, National Renewable Energy Laboratory (NREL) and Princeton University have evaluated the partial and complete deuteration of MA⁺ cations. 

This approach inhibits deprotonation and degradation, reduces the formation energy of the perovskite phase, improves grain growth, passivates defects, and restrains ion migration. As a result, perovskite solar cells incorporating this deuteration strategy achieved exceptional performance, including a high fill factor (FF) of 82.6% and a power conversion efficiency (PCE) of 25.6%.

A collaborative effort between NREL and CubicPV has yielded a perovskite minimodule with 24.0% certified efficiency, marking the first time a U.S. effort has set a record in the perovskite minimodule category.

Image credit: NREL

The researchers at NREL and at CubicPV made the minimodule consisting of multiple interconnected cells, with several steps in the fabrication sequence done at each location.