German scientists use NiOx to increase efficiency of perovskite solar cells

Scientists at Germany's Karlsruhe Institute of Technology (KIT) and the Innovation Lab in Heidelberg have developed a highly efficient hole conductor layer made of nickel oxide (NiOx) that can be deposited over a large area and leads to record efficiencies in solar cells with organometallic perovskites.

KIT scientists improve the efficiency of PSCs with NiOx image

The team achieved efficiencies of up to 16.1% for completely vacuum-processed perovskite solar cells. With inkjet-printed absorber layers, the scientists achieved an efficiency record of up to 18.5%. "Currently, deposition by rotary coating, for which efficiencies of more than 24% have been achieved, dominates development. However, this can practically not be transferred to large areas" says Tobias Abzieher, PhD student at KIT's Light Technology Institute (LTI).

Researchers use perovskite absorbers to utilize infrared light in solar cells

Researchers from Florida State University and Georgia Tech have been working on new ways for solar cells to absorb and use infrared light, a portion of the solar spectrum that is typically unavailable for solar cell technology.

“We’re working on a process to optimize the efficiency of solar cells,” said Assistant Professor of Chemistry and Biochemistry Lea Nienhaus. “The main drive is to optimize this process for solar applications”. The team has created a new approach for solar cells to facilitate a process called photon upconversion. In photon upconversion, two low energy photons are converted into one high-energy photon that emits visible light.

Achieving 26.0% efficient monolithic perovskite silicon tandem solar cells and analyzing the performance as a function of photocurrent mismatch

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%.

The influence of current mismatch on device performance in tandem perovskite silicon solar cells imageColored 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).

Collaborative team makes a major step forward in the search for stable and practical perovskite-based photovoltaic devices

A collaborative research team from Los Alamos National Laboratory, Rice University, Purdue University, Northwestern University, Institut FOTON CNRS UMR 6082 (France) and Argonne National Laboratory has created a number of hybrid perovskite solar cells with a FA0.7MA0.25Cs0.05PBI3 composition and measured them using a variety of techniques including grazing-incidence wide-angle x-ray scattering (GIWAXS) maps at the X-ray Science Division 8-ID-E x-ray beamline of the APS (an Office of Science user facility at Argonne).

casts light on new benefits of perovskite solar cells imageThe experimental setup (top left) and the corresponding light-induced lattice expansion effect, which leads to curing defects and relieving of lattice strain (bottom left) and as a result an increase in the open circuit voltage of a solar cell

In most of the cells, the researchers noted a substantial improvement in PCE from 18.5% to 20.5% under continuous light soaking with a 1-sun (100 mW/cm2) source as the lattice structure of the hybrid cells uniformly expanded. This expansion relieved local strains in the bulk material and better aligned the crystal planes, as evidenced by narrowing and uniform shifting of the Bragg peaks toward lower scattering values as seen by GIWAXS. The researchers explain that constant illumination generates electron-hole pairs in the perovskite material, decreasing the distortions of some bonds while elongating others, resulting in a generalized lattice expansion and relaxation. A similar phenomenon was seen with pure MAPbI3 thin films, suggesting that such lattice expansion under light is common for hybrid perovskite materials.

University of Toronto researchers create a more stable electron selective layer for PSCs and tandem solar cells

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.

University of Toronto researchers make Quantum Dots and Perovskite Solar Cells at 150°C image

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.