A strategy to enhance perovskite absorbers for all-perovskite tandem solar cells

• Tandem solar cells (TSCs), stacks of p-n junctions based on semiconductors with various bandgaps, are an extremely appealing energy service that could help to minimize carbon emissions.

Perovskites, earth-abundant products with a tunable bandgap, high charge-carrier mobilities, beneficial optoelectronic residential properties as well as long carrier diffusion lengths, could be specifically valuable for producing inexpensive and also very power-efficient TSCs for large-scale implementations.

To fabricate reliable all-perovskite TSCs, engineers need to be able to grow high-quality and consistent perovskite absorbers via condensation procedures. Absorbers are semiconducting layers inside solar cells that take in photons (i.e., light bits) and also excite electrons to develop photocurrent from sunlight. Thus far, nonetheless, an universal as well as reliable procedure to prepare perovskite absorbers for TSCs is still doing not have.

Researchers at Soochow University and also Sichuan University have just recently created a new method to create high-grade perovskite absorbers with grains in the micrometer scale and also prolonged carrier lifetimes. This method, presented in a paper released in Nature Energy, is based upon a close-space annealing (CSA) process, a heat-based technique that can be used to transform a material's chemical residential properties.

" Controllable formation plays a vital role in the formation of high-grade perovskites," Changlei Wang as well as his colleagues wrote in their paper. "Below, we report an universal CSA method that increases grain size, boosts crystallinity and prolongs carrier lifetimes in low-bandgap (low-Eg) as well as wide-bandgap (wide-Eg) perovskite films."

Remarkably, the CSA method created by Wang and his colleagues is global, as it can be related to perovskites with different bandgaps to produce high-grade absorbers with enlarged grains as well as longer service provider lifetimes. As part of their current study, the group showed its generalizability by successfully using it to prepare absorbers based on perovskites with different chemical compositions.

Basically, the newly presented technique entails growing perovskites via the CSA procedure, while managing the presence of residual solvents inside the intermediate-phase perovskites (i.e., the perovskite's type before the final annealing steps occur). The researchers found that this advertised the development of grains, combining neighboring crystals as solvents were slowly launched from the perovskites.

"By placing the intermediate-phase perovskite films with their faces in the direction of solvent-permeable covers during the annealing procedure, premium perovskite absorber layers are acquired with a slowed solvent releasing process, making it possible for fabrication of reliable single-junction perovskite solar cells (PVSCs) and also all-perovskite tandem solar cells," Wang and also his colleagues described in their paper.

In initial evaluations, the CSA approach created by the researchers made it possible for the development of very carrying out perovskite absorbers with both low and large bandgaps. These absorbers were after that made use of to fabricate 4-T and also 2-T all-perovskite TSCs that showed remarkable power conversion effectiveness.

"The very best PCEs of 21.51% and also 18.58% for single-junction low-Eg as well as wide-Eg PVSCs are accomplished and also hence ensure the fabrication of 25.15% efficiency 4-terminal as well as 25.05% performance 2-terminal all-perovskite tandem solar cells," Wang and also his colleagues wrote in their paper.

In the future, the CSA technique presented by this group of researchers could be made use of to produce far better absorbers for low-priced as well as reliable TSCs that are solely based upon perovskites. This can help with the large-scale execution of these highly appealing energy services. On the other hand, their research study can also inspire other research groups worldwide to devise similar fabrication strategies for generating highly executing perovskite absorbers.