Efficiency - Page 53

Researchers at EPFL in Switzerland have reported on the use of Flash Infrared Annealing (FIRA) to rapidly produce efficient, stable perovskite solar cells.

FIRA shares many characteristics with thermal annealing techniques already used to grow pure crystal phases for the semiconductor industry. It works by using a short IR pulse to rapidly nucleate a perovskite film from a precursor solution, without the need for a high-temperature scaffold. The high speed and relatively low processing temperatures mean that FIRA is compatible with large-area deposition techniques, like roll-to-roll processing. For PSCs, it could offer a practical route to scaling-up production.

A team of scientists in Japan has used carbon nanotubes to reliably create perovskite crystal layers free of defects and holes. Their findings could improve the performance of perovskite-based solar panels.

In this study, researchers led by Professor Keiko Waki at Tokyo Institute of Technology, Japan, found a way to bond carbon nanotubes (CNT) to perovskite to improve the latter's efficiency and stability.

Researchers from the University of California, San Diego and UCLA, Soochow University and Westlake University in China, and Marmara University in Turkey, have examined the surface defect-deactivation mechanism in perovskite solar cells using molecules found in tea, coffee and chocolate.

The collaborative team set out to delineate the molecular arrangements that constructively deactivate the surface defects in perovskite solar-cells. Highly-efficient metal-halide perovskite solar cells to date consist of polycrystalline perovskite film that often contains a high density of defects on the surface. These imperfections are the points for charge recombination, which is a major limiting factor in power conversion efficiency (PCE) and stability of perovskite solar cells. However, due to the ionic nature of the perovskite lattice, these defects can be passivated by surface treatment of perovskite with a small molecule.

Scientists from the universities of Cambridge and Oxford in the UK are investigating electron dynamics in perovskite solar cells in an effort to understand why such devices demonstrate such impressive conversion efficiency despite their thermal stability and durability problems.

The researchers said the morphology of the perovskite materials used for PV applications was not ideal for understanding the spatiotemporal charge-carrier dynamics which take place within them when photons are absorbed by methylammonium lead-iodide perovskite films.

Researchers at the Massachusetts Institute of Technology (MIT) have improved a transparent and conductive coating material by increasing its electrical conductivity by 10 times. When this coating material was integrated into a perovskite solar cell, it boosted the stability and efficiency of the solar cell.

'The goal is to find a material that is electrically conductive as well as transparent,' explained the team, which would be ‘'useful in a range of applications, including touch screens and solar cells.'

An international research team that included scientists from the University of Exeter, in the U.K., Switzerland's Ecole Polytechnique Federale de Lausanne (EPFL) and Saudi Arabia's Center of Excellence for Advanced Materials Research has reported hitting 21.6% perovskite solar cell efficiency by using concentrator photovoltaic technology.

PSC with a concentrator

A triple-cation based, n-i-p structured perovskite cell has reportedly been developed at low levels of solar concentration. According to the researchers, standard single-junction perovskite cells usually reach efficiencies of 21% but only in devices smaller than 1mm². 'The use of concentrator photovoltaics with a 0.81mm²-sized perovskite solar cell (PSC) further increased the efficiency levels up to 23.1% opening up a new line of research combining PSCs with low concentrating photovoltaic technologies,' the authors of the study wrote.

Scientists from Nanyang Technological University and Singapore's NTU, in collaboration with the University of Groningen (UG) in the Netherlands, have developed a method to analyze which pairs of materials in perovskite solar cells will harvest the most energy.

In their recent study, physicists Professor Sum Tze Chien from NTU and Professor Maxim Pshenichnikov from UG used extremely fast lasers to observe how an energy barrier forms when perovskite is joined with a material that extracts the electrical charges to make a solar cell.

A research group led by Prof. Liu Shengzhong from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) and Prof. Yang Dong at Shaanxi Normal University have developed high efficiency semi-transparent perovskite solar cells by using MoO₃ sandwiched gold nanomesh (MoO₃/Au/MoO₃) multilayer as the transparent electrode. Combined with a superior heterojunction silicon solar cell, a high efficiency four-terminal perovskite/silicon tandem solar cell was obtained.

Tandem/multijunction structure has been proven to be an effective way to break the Shockley-Queisser limit. To obtain a high efficiency tandem solar cell, the key is to fabricate transparent electrode with high conductivity as well as high transparency through a mild method.

Researchers from Helmholtz-Zentrum Berlin (HZB), headed by Prof. Susan Schorr and Dr. Joachim Breternitz, have achieved a breakthrough in understanding the crystalline structure of hybrid halide perovskites. The team investigated crystalline samples of methylammonium lead iodide (MAPbI₃), the most prominent representative of this class of materials, at the Diamond Light Source synchrotron (DLS) in the United Kingdom using high-resolution single-crystal diffraction. This approach provided data for a more in-depth analysis of the crystalline structure of this material.

They were also able to clarify, whether ferroelectric effects are possible at all in this hybrid halide perovskite. Ferroelectric domains can have favorable effects in solar cells and increase their efficiency. However, measuring this effect in samples is difficult - a null result can mean that there is either no ferroelectric effect or that the ferroelectric domains cancel one another's effects out.

Rice University researchers have overcome a major hurdle standing between perovskite-based solar cells and commercialization.

Through the strategic use of the element indium to replace some of the lead in perovskites, Rice materials scientist Jun Lou and his colleagues at the Brown School of Engineering say they're better able to engineer the defects in cesium-lead-iodide solar cells that affect the compound's band gap, a critical property in solar cell efficiency.