A brand new technique of producing perovskite photo voltaic cells solves earlier issues and gives gadgets with excessive effectivity and glorious stability, researchers on the Nationwide Renewable Power Laboratory (NREL) report. within the new difficulty of the journal Science.
The event of steady and environment friendly perovskites based mostly on a wealthy combination of bromine and iodine is taken into account vital for the event of tandem photo voltaic cells. The 2 components, nevertheless, are likely to separate when uncovered to gentle and warmth and subsequently restrict the voltage and sturdiness of a photo voltaic cell.
“This new progress technique can forestall part separation,” stated Kai Zhu, a senior scientist at NREL, principal investigator of the mission, and lead writer of the brand new paper “Compositional texture engineering for extremely steady broad bandgap perovskite photo voltaic cells.” His co-authors from NREL are Qi Jiang, Jinhui Tong, Rebecca Scheidt, Amy Louks, Robert Tirawat, Axel Palmstrom, Matthew Hautzinger, Steven Harvey, Steve Johnston, Laura Schelhas, Bryon Larson, Emily Warren, Matthew Beard, and Joseph Berry.
Different researchers concerned are on the College of Toledo.
The brand new technique addresses that drawback and produces a wide-bandgap photo voltaic cell with an effectivity larger than 20% and a 1.33-volt photovoltage and little change in effectivity over 1,100 hours of steady operation. at excessive temperatures. With this new technique, an all-perovskite tandem cell obtained an effectivity of 27.1% with a excessive photovoltage of two.2 volts and good operational stability.
Within the tandem cell, the slender bandgap layer is positioned on high of the broad bandgap layer. The distinction in bandgaps permits for extra photo voltaic spectrum to be captured and transformed into electrical energy.
Perovskite refers to a crystalline construction shaped by depositing chemical substances on a substrate. A excessive focus of bromine causes quicker crystallization of the perovskite movie and sometimes results in defects that cut back the efficiency of a photo voltaic cell. Varied methods have been tried to mitigate these points, however the stability of broad bandgap perovskite photo voltaic cells continues to be thought-about inadequate.
The newly developed technique builds on work that Zhu and his colleagues printed earlier this 12 months that reverse-engineered a typical perovskite cell. Utilizing this inverted architectural construction permits researchers to extend effectivity and stability and simply combine tandem photo voltaic cells.
The NREL-led staff used the identical structure and moved away from the standard approach of creating perovskites. The normal technique makes use of an antisolvent utilized to the chemical crystals to create a uniform perovskite movie. The brand new technique depends on so-called fuel quenching, the place a stream of nitrogen is blown by chemical substances. The end result addresses the issue of separating bromine and iodine, leading to a perovskite movie with improved construction and optoelectronic properties.
The antisolvent technique permits crystals to develop quickly and uniformly throughout the perovskite movie, crowding one another and resulting in defects the place grain boundaries meet. The fuel quenching course of, when utilized in perovskite chemical substances with excessive bromine, forces the crystals to develop collectively, tightly packed from high to backside, in order that they turn into like a single grain and cut back the variety of defects. The highest-down progress technique types a gradient construction, with extra bromine close to the floor and fewer within the bulk of the cell. The gas-quench technique is statistically extra reproducible than the antisolvent technique.
The researchers achieved an effectivity exceeding 20% for the broad bandgap layer and operational stability with lower than 5% degradation in 1,100 hours. Mixed with the decrease cell, the gadget reaches a 27.1% effectivity rating.
The researchers additionally examined argon and air because the drying fuel with related outcomes, indicating that the fuel quenching technique is a normal technique for enhancing the efficiency of broad bandgap perovskite photo voltaic cells.
The brand new progress technique reveals the potential of high-performance all-perovskite tandem gadgets and advances the event of different perovskite-based tandem architectures resembling these with silicon.
The US Division of Power’s Workplace of Photo voltaic Power Applied sciences funded the analysis.
NREL is the US Division of Power’s main nationwide laboratory for renewable power and power effectivity analysis and growth. NREL is operated for DOE by the Alliance for Sustainable Power LLC.
