Researchers from Chonnam National University, Chinese Academy of Sciences,  Indian Institute of Science (IISc) and Pennsylvania State University have introduced an alternative solar cell design fully based on inorganic perovskites. Their solar cells could be easier to fabricate on a large-scale, while also achieving promising power conversion efficiencies (PCEs).

The key objective of the recent work was to create new solar cells fully based on inorganic perovskites using a developed method that could be easy to up-scale. Ultimately, they fabricated their solar cells using hot-air and thermal evaporation deposition techniques that work at ambient conditions without requiring polar solvents (i.e., liquids containing both positive and negative charges).

A collaborative effort by researchers from the Centre for Hybrid and Organic Solar Energy (CHOSE), Department of Electronic Engineering at Tor Vergata University of Rome, Italy, the Department of Textile Engineering at the University of Guilan, Iran, GreatCell Solar Italia, Institute of Crystallography (IC-CNR), Italy, Department of Biological and Environmental Sciences and Technologies at the University of Salento, Italy and Institute of Nanotechnology (CNR NANOTEC), Italy, has resulted in the development of flexible perovskite solar cells with remarkable power conversion efficiencies (PCE) under white LED illumination.

The team achieved a maximum PCE of 28.9% at an illuminance of 200 lx and a record of 32.5% at 1000 lx, essentially converting a third of the incoming power (note that under 1 sun this figure for perovskite technology is less, i.e. one quarter).

Researchers at imec and University of Hasselt at Energyville, Belgium, recently set out to improve two key perovskite interfaces for solar cells for efficiency and lifetime.

The work focusses on the upper interface between the perovskite and the fullerene-C60 electron transport layer and the lower interface between the perovskite and the NiOx-based hole transport layer.

Researchers from China's University of Science and Technology (SUSTech), Chinese Academy of Sciences (CAS), City University of Hong Kong (CityU) and Korea University have developed an effective strategy to modify the Tin dioxide (SnO₂)/perovskite buried interface by passivating the buried defects in perovskite and modulating carrier dynamics via incorporating formamidine oxalate (FOA) in SnO₂ nanoparticles.

Tin dioxide (SnO₂) is a commonly used electron transport material for n-i-p-type perovskite solar cells (PSCs) due to its high light transmittance and electron mobility, suitable energy levels, good stability under UV irradiation, and it can be processed at low temperatures. The buried interface of perovskite/SnO₂ plays a major role in achieving high efficiency and stability. However, the non-exposed buried interface is challenging to study and manipulate.

Researchers from the University of Toledo, NREL and the University of Colorado Boulder have designed highly efficient, bifacial, single-junction perovskite solar cells based on a p-i-n (or inverted) architecture. In this work, the team showed that bifacial perovskite photovoltaics technology has the potential to outperform its monofacial counterparts.

The team used optical and electrical modeling to guide the optimization of the transparent conducting rear electrode and perovskite absorber layer using a p-i-n device architecture, achieving a high bifaciality of about 91%–93% and a high front-side illumination PCE of over 23%. Under concurrent bifacial measurement conditions, the equivalent, stabilized bifacial power output densities were 26.9, 28.5, and 30.1 mW/cm² under albedos of 0.2, 0.3, and 0.5, respectively. 

Researchers from Switzerland's Ecole Polytechnique Fédérale de Lausanne (EPFL), Chinese Academy of Sciences (CAS) and Peking University have developed a perovskite solar cell with a 2D/3D heterojunction architecture.

The cell uses a 2D perovskite layer at the interface between the perovskite and the hole transport layer, which the researchers said can improve charge-carrier transport/extraction while suppressing ion migration. Cells with this architecture usually exhibit large exciton binding energies and are generally more stable than conventional 3D devices due to the protection provided by the organic ligands.

Researchers at Huazhong University of Science and Technology, Russian Academy of Sciences, Okinawa Institute of Science and Technology Graduate University (OIST) and Shanghai Jiao Tong University have developed a design strategy that could reduce defects in FAPbI₃-based solar cells, improving their power efficiency. This strategy involves the application of an additive and a coating agent to the perovskite films integrated in the solar cells.

"Power conversion efficiencies of inverted perovskite solar cells (PSCs) based on methylammonium- and bromide-free formamidinium lead triiodide (FAPbI₃) perovskites still lag behind PSCs with a regular configuration," Rui Chen, Jinan Wang, and their colleagues wrote in their paper. "We improve the quality of both the bulk and surface of FA_0.98Cs_0.02PbI₃ perovskite films to reduce the efficiency gap."

Researchers from Thailand's Mahidol University, Chiang Mai University, the Center of Excellence for Innovation in Chemistry (PERCH-CIC) and the National Metal and Materials Technology Center (MTEC) have developed triple-cation perovskite solar cells for low-light applications using a manufacturing process based on antisolvent deposition and vacuum thermal annealing (VTA).

“VTA leads to compact, dense, and hard morphology while suppressing trap states at surfaces and grain boundaries, which are key culprits for exciton losses,” the team stated, emphasizing the importance of the second step to produce a high quality perovskite layer. “As indoor light intensity is at least 300 times lower than that of sunlight, dense and homogeneous perovskite formation enticed by vacuum thermal annealing is valuable.”

In two separate studies, researchers report novel methods that enable the fabrication of high-performance perovskite-silicon tandem solar cells with power conversion efficiencies exceeding 30%. 

Combining perovskite and silicon solar cells into a tandem device could provide a promising path toward high-performance PVs. Here, in the two separate studies, researchers present different strategies for developing perovskite-silicon tandem solar cells with a PCE exceeding 30%. In one study, Xin Yu Chin from Ecole Polytechnique Fédérale de Lausanne (EPFL) and colleagues showed that the uniform deposition of the perovskite top cell on a silicon bottom cell featuring micrometric pyramids – the industry standard configuration – can facilitate high photocurrents in tandem solar cells.

Printable planar carbon electrodes are emerging as a promising replacement for thermally evaporated metals as the rear contact for perovskite solar cells (PSCs). However, the power conversion efficiencies (PCEs) of the state-of-the-art carbon-electrode PSC (c-PSC) noticeably lag behind their metal-electrode counterparts. Recently, researchers from Friedrich-Alexander-Universität Erlangen-Nürnberg have proposed a hole-transporting bilayer (HTbL) configuration to improve the fill factor and the open-circuit voltage of carbon electrode PSCs (c-PSCs). 

The HTbL was prepared by sequentially blade coating two organic semiconductors between perovskite and carbon, with the outer HTL enhancing hole extraction to carbon, while the inner HTL mitigates perovskite surface recombination. Consequently, the fully printed c-PSCs with HTbL outperformed those with single HTL, and a stabilized champion PCE of 19.2% was achieved compared with that of 17.3%.