Efficiency - Page 2

The certified efficiency of 1 cm² scale all-perovskite tandem solar cells tends to lag behind that of their small-area (~0.1 cm2) counterparts. This performance deficit originates from inhomogeneity in wide-bandgap (WBG) perovskite solar cells (PSCs) at a large scale. The inhomogeneity is thought to be introduced at the bottom interface and within the perovskite bulk itself. 

Researchers from Nanjing University, Jilin University, University of Cambridge, University of Victoria, The Australian National University, Chinese Academy of Sciences (CAS) and Renshine Solar (Suzhou) have reported an all-perovskite tandem solar cell based on a wide-bandgap top perovskite cell with a 20.5% efficiency. 

Researchers at the University of Tsukuba and Kyoto University have studied the internal properties of low-cost materials used in perovskite solar cells that use HND-2NOMe, a replacement hole-transport material to spiro-OMeTAD, using electron spin resonance (ESR) to analyze these materials at a microscopic level.

Chemical structures of hole-transport materials spiro-OMeTAD and HND-2NOMe. Image from: Communications Materials

The results clarify the underlying causes for reduced device performance, despite high local charge mobility, offering critical insights for designing improved solar cells. 

Researchers from China's Tianshui Normal University have reported a grain regeneration and passivation approach that can decrease the recombination loss of the perovskite layer/charge transfer layer interface and the grain border. 

Device manufacturing process. Image from: Scientific Reports

The team relies on guanidine iodide (GAI) treatment of perovskite films for this new approach. Unlike most methods that use GAI for post-treatment of the perovskite layer or add GAI into the perovskite precursor solution, this work uses GAI for pre-treatment before spin coating the perovskite layer. It can effectively passivate surface defects and increase the grain size of perovskite films by controlling the crystallization process. 

Researchers from Konkuk University, Tokyo University of Agriculture and Technology and Nanoenics have reported an improved crystallization of hybrid perovskite films achieved through the addition of a potent antioxidant derived from garlic, known as allicin. Oxidation of hybrid perovskite composed of organic–inorganic materials can cause significant problems in performance and stability of perovskite solar cells (PSCs), because the hybrid perovskite oxidation induces considerable decrease in crystallinity and quality of hybrid perovskites.

Defect sites within the hybrid perovskite film, which arise during annealing and ageing processes, were found to be effectively managed by the antioxidant properties of allicin, particularly at elevated temperatures. Acting as an in situ encapsulator for the hybrid perovskite, the antioxidant efficiently regulated defect sites by supplying protons and neutralizing free radicals. 

Researchers from the  Chinese Academy of Sciences (CAS) and Zhejiang University have developed a highly passivated TOPCon bottom cell, achieving perovskite/silicon tandem solar cells (TSCs) with high open-circuit voltages (VOCs) and excellent efficiencies. 

The structure and performance of tandem devices with highly passivated TOPCon bottom cells. Image by Ningbo Institute of Materials Technology and Engineering (NIMTE) 

Numerous defects at the fragile silicon oxide/c-Si interface and the weak field-effect passivation on textured substrates reduce the VOCs of current TOPCon silicon solar cells, thus limiting their application for high-performance perovskite/silicon TSCs. In this study, the researchers prepared highly passivated p-type TOPCon structures and double-sided TOPCon bottom cells on industrial textured wafers via industry-compatible fabrication methods, including ambient-pressure thermal oxidation and in situ plasma-enhanced chemical vapor deposition.

Researchers at the Korea Advanced Institute of Science and Technology (KAIST), Yonsei University, Gwangju Institute of Science and Technology (GIST) and Korea Institute of Ceramic Engineering and Technology (KICET) have reported a high-efficiency and high-stability organic-inorganic hybrid solar cell production technology that maximizes near-infrared light capture beyond the existing visible light range.

The research team suggested a hybrid next-generation device structure with organic photo-semiconductors that complements perovskite materials limited to visible light absorption and expands the absorption range to near-infrared. In addition, they focused on a common issue that mainly occurs in the structure and developed a solution to this problem by introducing a dipole layer - a thin material layer that controls the energy level within the device to facilitate charge transport and forms an interface potential difference to improve device performance.

Researchers from Australia’s University of New South Wales (UNSW) Sydney have developed a defects passivation strategy for chloride-iodide-based perovskite. The team targeted the hard-to-avoid local defects in chloride-iodide-based perovskites, using two organic halide passivators named 4-chlorobenzylammonium chloride and 4-chlorobenzylammonium bromide. 

The scientists passivate both the surface and bulk of the perovskite thin film. The surface of the perovskite thin film is passivated with the bulky organic benzylammonium cations. The bulk of the perovskite thin film is passivated with the diffusion of chlorine or bromine. 

Researchers from King Abdullah University of Science and Technology (KAUST) and  Helmholtz-Zentrum Berlin (HZB) have developed a perovskite-silicon tandem solar cell that achieves efficient charge extraction and interface passivation. The team improved the performance of blade-coated tandems by introducing 2D perovskite layers at the bottom interface. 

Image credit: Joule

These modifications enhanced the blade-coated tandem performance to a certified PCE of 31.2%, owing to efficient charge extraction and interface passivation. This work demonstrates the efficiency potential for scalable ink-based fabrication, emphasizing stability and manufacturability, which are crucial for the widespread adoption and commercial success of this promising photovoltaic (PV) technology.

Researchers at Chinese Academy of Sciences (CAS) have fabricated an intermediate recombination layer (IRL) featuring a heavily doped boron/phosphorus polysilicon tunneling junction, with tunnel oxide passivated contact (TOPCon) silicon cells serving as the bottom cell for perovskite/TOPCon tandem solar cells (TSCs). 

In perovskite/silicon TSCs, the IRL is an important structure electrically connecting the top-side perovskite and bottom-side silicon sub-cells, significantly influencing the overall device performance. The traditional IRL often uses ITO materials to ensure high transmittance and good electrical properties, which, however, usually leads to issues such as sputtering damage and low temperature process limitations.

Interface engineering plays a significant role in the constant improvement in the performance of perovskite photovoltaics, but such devices still suffer from several issues, including unavoidable open circuit voltage (VOC) losses. Now, an international team of researchers from Università Degli Studi Di Pavia, King Abdullah University of Science and Technology (KAUST), Chinese Academy of Sciences (CAS), University of Cambridge, Istituto Italiano di Tecnologia (IIT), Slovak Academy of Sciences and Imperial College London have proposed a different approach by creating a photo-ferroelectric perovskite interface. 

Graphical representation of the 2D/3D/2D perovskite heterostructure. Image from: Nature Communications

By engineering an ultrathin ferroelectric two-dimensional perovskite (2D) which sandwiches a perovskite bulk, the scientists exploited the electric field generated by external polarization in the 2D layer to enhance charge separation and minimize interfacial recombination. As a result, they observed a net gain in the device VOC reaching 1.21 V, the highest value reported to date for highly efficient perovskite PVs, leading to a champion efficiency of 24%.