In September 2019, a research team led by Prof. Steve Albrecht from the HZB (in close collaboration with Kaunas University of Technology in Lithuania) announced a tandem solar cell with certified efficiency of 23.26% that combines the semiconducting materials perovskite and CIGS. Now, the team shares further details on these cells and states that an unnamed Japanese manufacturer has acquired the rights to produce them.

The scientists said the self-assembling material used for the cell is made of molecules based on carbazole head groups with phosphonic acid anchoring groups, and consists of 1-2nm of self-assembled monolayers deposited on the surface of the perovskite by dipping it into a diluted solution.

A Cornell-led team of scientists has discovered a crystalline material with ultralow thermal conductivity, which could lead to the design of novel energy conversion materials and devices.

After studying a popular hybrid perovskite and identifying the mechanisms for its low thermal conductivity, Zhiting Tian, assistant professor of mechanical and aerospace engineering at Cornell, turned her attention to a hybrid perovskite analogue, methylammonium bismuth iodide (CH₃NH₃)₃Bi₂I₉, which she hypothesized would have an even lower thermal conductivity because of the unique disconnected structure of its inorganic molecules.

An international team of researchers, including ones from Penn State, Columbia University, University of Toledo, Northeastern University in the U.S and Carl von Ossietzky University in Germany, designed next-gen solar cells that mimic photosynthesis with a biological material, by adding the protein bacteriorhodopsin (bR) to perovskite solar cells.

Power conversion efficiency (PCE) distribution of bR-incorporated PSC based on statistics of 15 devices, with average efficiency of 16.34 %. Image from ACS article

'These findings open the door for the development of a cheaper, more environmentally friendly bioperovskite solar cell technology,' said Shashank Priya, associate vice president for research and professor of materials science at Penn State. 'In the future, we may essentially replace some expensive chemicals inside solar cells with relatively cheaper natural materials.'

Researchers at the University of Rome Tor Vergata in Italy and Russia's NUST MISIS institute have investigated how cells containing two-dimensional titanium-carbide MXene support layers could improve perovskite solar cell performance.

To obtain good power conversion within a perovskite solar cell, all layers and layer interfaces within the cell must have good compatibility. Typical cells contain the active perovskite material sandwiched between two charge transport layers, which are then adjacent to their corresponding electrodes. Support layers may also be added. Charge mobility, energy barriers, interface energy alignment, and interfacial vacancies all impact compatibility and subsequent cell performance and stability. Thus, engineering well-suited interfaces with the cell is paramount to cell success and long-term stability, an important criterion for potential commercialization.

Researchers from the Ulsan Institute of Science and Technology (UNIST) have demonstrated a new method of fabricating perovskite-on-silicon tandem devices, using a transparent conductive adhesive (TCA) to combine the two cells. The scientists have developed devices with demonstrated efficiencies of 19.4%, and propose methods to bring that up to over 24% using existing technology.

While the efficiency is still well below the 28% record for a perovskite/silicon tandem cell set by Oxford PV, the UNIST group says its method is far simpler to manufacture than previous concepts. 'It is meaningful to develop an attached tandem solar cell unlike the conventional tandem solar cell with stacked structure,' said UNIST's In Young Choi, lead author of the study. 'We have observed that the TCA effectively connects the different light-absorbing layers.'

A team led by Prof. Steve Albrecht from the HZB has announced a new world-record: a tandem solar cell with certified efficiency of 23.26% that combines the semiconducting materials perovskite and CIGS. One reason for this success lies in the cell's intermediate layer of organic molecules: they self-organize to cover even rough semiconductor surfaces. Two patents have been filed for these layers.

Perovskite-based solar cells have experienced an incredibly rapid increase in efficiency over the last ten years. The combination of perovskites with classical semiconductor materials such as silicon and copper-indium-gallium-selenide (CIGS) compounds in tandem solar cells promises low-cost, high-performance solar modules for the future. However, losses at the electrodes between the two semiconductors considerably reduce the efficiency.

Solliance and U.S-based MiaSolé announced a new record - power conversion efficiency of 23% on a flexible tandem solar cell: a top flexible semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

This achievement comes only 9 months after the January 2019 announcement by Solliance and MiaSolé regarding a flexible solar cell with an impressive power conversion efficiency of 21.5%. The solar cell, similarly to this newly announced one, combined two thin-film solar cell technologies into a 4 terminal tandem solar cell stack: a top flexible semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

German university the Karlsruhe Institute of Technology (KIT), the Center for Solar Energy and Hydrogen Research Baden-Würtetemburg (ZSW) and CIGS module manufacturer Nice Solar Energy have announced an ambition to design tandem PV modules based on CIGS and perovskite, which can theoretically achieve efficiencies well above 30%.

The joint 'Capitano' project will run for three years and has received more than €5 million from Germany's Federal Ministry for Economic Affairs and Energy. The aim of the project is to develop cells with stable higher efficiencies, which can be interconnected to form efficient tandem solar modules.

Researchers from Helmholtz-Zentrum Berlin (HZB), Eindhoven University of Technology and Technical University Berlin have combined rear junction silicon heterojunction bottom cells with p'i'n perovskite top cells into highly efficient monolithic tandem solar cells with a power conversion efficiency (PCE) of 26.0%.

Colored cross sectional SEM image of the top cell (upper panel) and back side of the bottom cell (lower panel) of a typical monolithic tandem solar cell used in this work. (b) schematic device layout of the tandem architecture utilized in this work.

Starting from a certified efficiency of 25.0%, further improvements have been reached by reducing the current mismatch of the certified device. The top contact and perovskite thickness optimization allowed increasing the JSC above 19.5 mA cm'2, enabling a remarkable tandem PCE of 26.0%, however with a slightly limited fill factor (FF).

Researchers at the University of Toronto have designed a method of growing a more stable electron selective layer for perovskite solar cells and tandem solar cells combining crystalline silicon with perovskite.

Perovskite raw materials can be mixed into a liquid in a kind of 'solar ink.' This solar ink could be printed onto glass, plastic or other materials with a relatively simple inkjet printing process. However, in order to generate electricity, electrons excited by solar energy from perovskite cells must be extracted from a layer of quantum dots that is held together by a passivation layer. Some types of quantum dots are known to change their 3D structure even at room temperature, making them transparent and ineffective. This passivation layer is also known to break down at temperatures above 100°C. The team's breakthrough made both quantum dots and perovskites more stable when combined than they are separated and the solar cell combining of Perovskite material and quantum dots achieved 20.1% efficiency.