Takeshi Sano

We developed a non-Phen electron-transporter named DPmPy-BP. With Ag as an air-stable EIL, DPmPy-BP exhibited superior electron-injection, achieving EQE of 20% and LT50 of 17 000 h at 1000 cd m⁻², outperforming the corresponding Phen/Ag device.

We have introduced a three-component light-emitting layer consisting of a host, a phosphorescent assist dopant, and a phosphorescent emitter to simultaneously realize high efficiency and long lifetime in NIR organic LEDs. An efficient energy transfer between the two phosphorescent materials was observed with 1 wt% doping ratio of the NIR emitter, significantly enhancing the external quantum efficiency reaching 10.5% with an emission peak at 769 nm. The device showed a low drive voltage and a long operational lifetime, with a luminance decay of less than 11% from the initial value after 4800 h under accelerated conditions of 100 mA cm⁻².

In this study on perovskite solar cells (PVSCs), we incorporate N-benzylhydroxylamine (N-BzHoA) as an additive into the precursor solution. The addition of N-BzHoA suppressed the formation of unwanted PbI₂ and δ-phase perovskite without affecting the band gap, confirming uniform and large grains in the perovskite film. The fabricated inverted PVSCs exhibited remarkably improved properties compared to the control device, with a power conversion efficiency of 17.49%, reduced hysteresis, and more than 89% retention of the initial capacity after 100 h of light exposure. Thus, this study highlights the effectiveness of N-BzHoA as an effective additive for inverted PVSCs.

Organic–inorganic halide perovskite solar cells (PVSCs) are considered a promising emerging photovoltaic technology that offer exceptional optoelectronic properties and the potential for economic solar energy conversion. Additive engineering‐based fabrication processes can achieve highly efficient and stable PVSCs that feature well‐controlled perovskite layers with a dense, uniform, “black” α‐phase crystal structure, as well as large grains and few defects. In this study, several hydroxylamine derivatives are introduced as additives to FAPbI₃ precursor solutions to investigate their effects on the performance of PVSCs. The addition of hydroxylamine derivatives suppresses the formation of the unwanted δ‐phase and lead iodide, while the α‐phase cubic structure is preferentially formed without changing the bandgap of FAPbI₃. Additionally, the additive‐treated perovskite films show improved stability compared with those without additives. Moreover, using X‐ray diffraction and X‐ray photoelectron spectroscopy analyses, it is discovered that the hydroxylamine‐based additives are not incorporated in the crystal lattices but rather resided on the surface or grain boundaries. Notably, the inverted PVSCs added with N‐methylhydroxylamine exhibit an improved power conversion efficiency, higher stability, and minimal hysteresis.

Low‐temperature‐processed inverted perovskite solar cells (PVSCs) attract increasing attention because they can be fabricated on both rigid and flexible substrates. For these devices, hole‐transporting layers (HTLs) play an important role in achieving efficient and stable inverted PVSCs by adjusting the anodic work function, hole extraction, and interfacial charge recombination. Here, the use of a low‐temperature (≤150 °C) solution‐processed ultrathin film of poly[(9,9‐dioctyl‐fluorenyl‐2,7‐diyl)‐co‐(4,4′‐(N‐(4‐secbutylphenyl) diphenylamine)] (TFB) is reported as an HTL in one‐step‐processed CH₃NH₃PbI₃ (MAPbI₃)‐based inverted PVSCs. The fabricated device exhibits power conversion efficiency (PCE) as high as 20.2% when measured under AM 1.5 G illumination. This PCE makes them one of the MAPbI₃‐based inverted PVSCs that have the highest efficiency reported to date. Moreover, this inverted PVSC also shows good stability, which can retain 90% of its original efficiency after 30 days of storage in ambient air.

Semitransparent organic solar cells (ST-OSCs) exhibit highly promising applications to develop integrated photovoltaics and power-generating windows. However, the development of ST-OSCs is significantly lagging behind opaque OSCs, especially for all small-molecule ST-OSCs. Here, four unique squaraines dyes (IDPSQ, SQ-BP, D-BDT-SQ, and AzUSQ) were successfully used as donors in ST-OSCs, whose colors can be tuned from purple to blue, green, and dark green, respectively. While using ultrathin Ag as a transparent electrode, the ST-OSCs fabricated using IDPSQ:PC₇₁BM, SQ-BP:PC₇₁BM, D-BDT-SQ:PC₇₁BM, and AzUSQ:PC₇₁BM yield power conversion efficiencies (PCEs) of 2.96, 4.36, 4.91, and 1.71%, respectively, and their colors are purple, cyan, brown, and light brown, respectively. Compared to their opaque OSCs (PCEs of 3.95, 5.45, 5.84, and 1.91%, respectively), the reduction in the PCEs are as low as 25, 20, 16, and 10%, respectively. Furthermore, each of these ST-OSCs exhibit good average visible transmittance (AVT) of 25–30%, favorable CIE color coordinates, and a color rendering index (CRI) of 71–97%. Finally, by changing the thickness of the Ag electrode, an impressive PCE of 4.9% along with an AVT of 25% and a CRI of 97% can be obtained in D-BDT-SQ:PC₇₁BM-based ST-OSCs, which is the highest PCE among all small-molecule ST-OSCs.

Organic solar cells (OSCs) are considered as a promising next-generation photovoltaic technology because of their light weight, flexibility, and the potential of roll-to-roll fabrication. However, the relatively large energy loss (E_loss) from the optical bandgap (E_g) of the absorber to the open-circuit voltage (V_oc) of the device hinders further improvement of the PCEs of OSCs. Here, we report efficient non-fullerene all-small-molecule organic solar cells (NF all-SMOSCs), using DR3TBDTT and O-IDTBR as the donor and acceptor, respectively. We obtain a high electroluminescence yield (EQE_EL) value of up to ∼4 × 10⁻⁴ corresponding to a 0.21 eV non-radiative recombination loss, which is the smallest value for bulk-heterojunction (BHJ) OSCs so far. As a result, a low E_loss of 0.54 eV and a considerably high V_oc of 1.15 V are obtained for BHJ NF all-SMOSCs.

Introduction of diCN-substitution can lower the HOMO and improve the miscibility between diCN-USQ and PC₇₁BM, leading to higher PCE.