Researchers have designed and synthesized a new organic semiconductor for organic solar cells (OSCs). By adding specific side units to their structure, they achieved separation between the frontier molecular orbitals, leading to lower exciton binding energy and increased power conversion efficiency.
Researchers have designed and synthesized a new organic semiconductor for organic solar cells . By adding specific side units to their structure, they achieved separation between the frontier molecular orbitals, leading to lower exciton binding energy and increased power conversion efficiency.
This tuning of the design of an acceptor component is expected to increase the performance of OSCs leading to more effective large-scale photovoltaic systems and new devices. Organic solar cells -- promising alternatives to traditional inorganic solar cells -- have many features that make them key players in a greener future. One of these features is tunable chemistry, which allows scientists to precisely adjust or modify the properties of chemical systems to achieve desired outcomes. Now, researchers from Japan have tuned them to increase power conversion efficiency.researchers from Osaka University have reported a new organic semiconductor that gives better power conversion efficiency than the accepted standard. OSCs are light and flexible and can be produced on a large scale for relatively low cost. They are therefore highly promising for applications such as agrivoltaics where large areas of land are used to simultaneously grow crops and turn the sun's energy into electricity. Generally, OSCs contain two organic semiconductors, one to transport charge carriers known as electrons and one to transport the other carriers known as holes . A current flows in a semiconductor when excitons -- combination of an electron and a positive hole -- are split into these carriers giving electron-hole pairs. Excitons are bound tightly together, but sunlight with enough energy can cause them to dissociate and generate a current. "Reducing the amount of energy needed to break up an exciton -- the exciton binding energy -- makes it easier to convert the light into the desired current," explains lead author of the study Seihou Jinnai."We therefore focused on the factors that contribute to the binding energy, one of which is the distance between the electron and the hole. If this is increased, then the binding energy should decrease." The researchers therefore designed a molecule with side units that had the effect of separating the parts of the molecule that accommodate the electron and the hole. The synthesized molecule was used as an acceptor in a bulk heterojunction OSC along with a donor material, and the system showed increased power conversion efficiency compared with the accepted standard. The molecule was also tested as the single component of an OSC and showed better conversion of light to current. "The molecule we designed shows that the nature of side units in acceptor molecules is key to the exciton behavior and its efficiency as a result," says senior author Yutaka Ie."This result provides an important demonstration of what can be achieved by tuning chemistry for OSCs applications." The findings indicate the potential of rational design of organic semiconductors and are expected to lead to new devices including high-performance OSCs and wavelength-selective transparent OSCs. General improvements in performance are also expected to enhance the potential of OSCs in large-scale photovoltaic applications, naturally leading to green energy alternatives.Kai Wang, Seihou JINNAI, Takumi Urakami, Hirofumi Sato, Masahiro Higashi, Sota Tsujimura, Yasuhiro Kobori, Rintaro Adachi, Akira Yamakata, Yutaka Ie. Nonfullerene Acceptors Bearing Spiro‐Substituted Bithiophene Units in Organic Solar Cells: Tuning the Frontier Molecular Orbital Distribution to Reduce Exciton Binding EnergyOrganic semiconductors are materials that find applications in various electronic devices. Exciton binding energy is an important attribute that influences the behavior of these materials. Now, ... Researchers have achieved a breakthrough power-conversion efficiency of 19.31% with organic solar cells , also known as polymer solar cells. This remarkable binary OSC efficiency will ... Organic solar cells show great promise for clean energy applications. However, photovoltaic modules made from organic semiconductors do not maintain their efficiency for long enough under sunlight ... A research team has set a new record in the power conversion efficiency of solar cells made using perovskite and organic materials. Their latest work demonstrated a power conversion efficiency of ...Research Reveals Reality of Ice Age Teen Puberty'Some Pterosaurs Would Flap, Others Would Soar' -- New Study Further Confirms the Flight Capability of These Giants of the Skies
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