Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
Quasi‐2D perovskites are attractive because of their improved stability compared with 3D perovskites counterparts; however, they suffer from poor performance due to the insulating organic cation spacers. To resolve this issue, a strategy of replacing the insulating spacer with conducting spacer is proposed which successfully converts the spacer from a charge‐transporting “barrier” to charge‐transporting “bridge.” Specifically, an alkyl linker‐free, fully conjugated aromatic 2,2′‐biimidazolium (BIDZ) cation is introduced as a spacer to compose quasi‐2D perovskites. Density functional theory (DFT) simulation results show that the lowest unoccupied molecular orbital (LUMO) level localizes on BIDZ and the highest occupied molecular orbital (HOMO) level is on the perovskite. However, both HOMO and LUMO levels localize on perovskite slabs for the well‐known phenethylammonium (PEA)‐based 2D perovskites. The strong electronic coupling between BIDZ and 3D perovskite slabs improves carrier mobilities even for a low‐weak‐crystallinity and random‐orientated quasi‐2D perovskite film. As a result, a remarkable power conversion efficiency up to 11.4% (
n = 5) is achieved, which is much higher than that of PEA‐based random‐orientated quasi‐2D perovskites with the same processing condition (6.5%). The strategy paves the way to highly efficient and stable quasi‐2D perovskites solar cells through designing new organic spacer cations. -
Abstract Semitransparent (ST) photovoltaics (PVs) with selective absorption in the UV or/and near‐infrared (NIR) range(s) and reduced energy losses, are critical for high‐efficiency solar‐window applications. Here, a high‐performance tandem ST‐PV with selected absorption in the desirable regions of the solar spectrum is demonstrated. An ultralarge‐bandgap perovskite film (FAPbBr2.43Cl0.57,
E g≈ 2.36 eV) is first developed to fulfil efficient selective absorption in the UV region. After optimization, the corresponding ST single junction (SJ) PV exhibits an averaged transmittance (AVT) of ≈68% and an efficiency of ≈7.5%. By sequentially reducing the visible absorbing component in a low‐bandgap organic bulk‐heterojunction layer, an ST‐PV with selective absorption in the NIR is achieved with a power conversion efficiency (PCE) of 5.9% and a high AVT of 62%. The energy loss associated with the SJ ST‐PVs is further reduced with a tandem architecture, which affords a high PCE of 10.7%, an AVT of 52.91%, and a light utilization efficiency up to 5.66%. These results represent the best balance of AVT and PCE among all ST‐PVs reported so far, and this design should pave the road for solar windows of high performance. -
Abstract Composition engineering is a particularly simple and effective approach especially using mixed cations and halide anions to optimize the morphology, crystallinity, and light absorption of perovskite films. However, there are very few reports on the use of anion substitutions to develop uniform and highly crystalline perovskite films with large grain size and reduced defects. Here, the first report of employing tetrafluoroborate (BF4−) anion substitutions to improve the properties of (FA = formamidinium, MA = methylammonium (FAPbI3)0.83(MAPbBr3)0.17) perovskite films is demonstrated. The BF4−can be successfully incorporated into a mixed‐ion perovskite crystal frame, leading to lattice relaxation and a longer photoluminescence lifetime, higher recombination resistance, and 1–2 orders magnitude lower trap density in prepared perovskite films and derived solar cells. These advantages benefit the performance of perovskite solar cells (PVSCs), resulting in an improved power conversion efficiency (PCE) of 20.16% from 17.55% due to enhanced open‐circuit voltage (
V OC) and fill factor. This is the highest PCE for BF4−anion substituted lead halide PVSCs reported to date. This work provides insight for further exploration of anion substitutions in perovskites to enhance the performance of PVSCs and other optoelectronic devices. -
Abstract Extremely high power conversion efficiencies (PCEs) of ≈20–22% are realized through intensive research and development of 1.5–1.6 eV bandgap perovskite absorbers. However, development of ideal bandgap (1.3–1.4 eV) absorbers is pivotal to further improve PCE of single junction perovskite solar cells (PVSCs) because of a better balance between absorption loss of sub‐bandgap photons and thermalization loss of above‐bandgap photons as demonstrated by the Shockley–Queisser detailed balanced calculation. Ideal bandgap PVSCs are currently hindered by the poor optoelectronic quality of perovskite absorbers and their PCEs have stagnated at <15%. In this work, through systematic photoluminescence and photovoltaic analysis, a new ideal bandgap (1.35 eV) absorber composition (MAPb0.5Sn0.5(I0.8Br0.2)3) is rationally designed and developed, which possesses lower nonradiative recombination states, band edge disorder, and Urbach energy coupled with a higher absorption coefficient, which yields a reduced
V oc,loss(0.45 V) and improved PCE (as high as 17.63%) for the derived PVSCs. This work provides a promising platform for unleashing the complete potential of ideal bandgap PVSCs and prospects for further improvement. -
Abstract Research at the University of Washington regarding organic semiconductors is reviewed, covering four major topics: electro‐optics, organic light emitting diodes, organic field‐effect transistors, and organic solar cells. Underlying principles of materials design are demonstrated along with efforts toward unlocking the full potential of organic semiconductors. Finally, opinions on future research directions are presented, with a focus on commercial competency, environmental sustainability, and scalability of organic‐semiconductor‐based devices.