High-purity precursor materials are vital for high-efficiency perovskite solar cells (PSCs) to reduce defect density caused by impurities in perovskite. In this study, we present aqueous synthesized perovskite microcrystals as precursor materials for PSCs. Our approach enables kilogram-scale mass production and synthesizes formamidinium lead iodide (FAPbI ₃ ) microcrystals with up to 99.996% purity, with an average value of 99.994 ± 0.0015%, from inexpensive, low-purity raw materials. The reduction in calcium ions, which made up the largest impurity in the aqueous solution, led to the greatest reduction in carrier trap states, and its deliberate introduction was shown to decrease device performance. With these purified precursors, we achieved a power conversion efficiency (PCE) of 25.6% (25.3% certified) in inverted PSCs and retained 94% of the initial PCE after 1000 hours of continuous simulated solar illumination at 50°C.

A new series of phosphorescent platinum(II) cyclometalated complexes with distinct electronic structures has been developed by simple tailoring of the phenyl ring of ppy (Hppy = 2-phenylpyridine) with various main-group moieties in [Pt(ppy-X)(acac)] (X = B(Mes)₂ , SiPh₃ , GePh₃ , NPh₂ , POPh₂ , OPh, SPh, SO₂Ph substituted at the para position). Their distinctive electronic characters, resulting in improved hole-injection/hole-transporting or electron-injection/electron-transporting features, have confined/consumed the electrons in the emission layer of organic light-emitting diodes (OLEDs) to achieve good color purity and high efficiency of the devices. The maximum external quantum efficiency of 9.52%, luminance efficiency of 30.00 cd A⁻¹ and power efficiency of 8.36 lm W⁻¹ for the OLEDs with Pt-B (X = B(Mes)₂ ) as the emitter, 8.50%, 29.74 cd A⁻¹ and 19.73 lm W⁻¹ for the device with Pt-N (X = NPh₂ ), 7.92%, 22.06 cd A⁻¹ and 13.64 lm W⁻¹ for the device with Pt-PO (X = POPh₂ ) as well as 8.35%, 19.59 cd A⁻¹ and 7.83 lm W⁻¹ for the device with Pt-SO₂ (X = SO₂Ph) can be obtained. By taking advantage of the unique electronic structures of the Pt-Ge (X = GePh₃ ) and Pt-O (X = OPh) green emitters and the intrinsic property of blue-emitting hole-transport layer of 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), single-dopant white OLEDs (WOLEDs) can be developed. These simple WOLEDs emit white light of very high quality (CIE at (0.354, 0.360), CRI of ca. 97 and CCT at 4719 K) even at high brightness (>15000 cd m⁻²) and the present work represents significant progress to address the bottle-neck problem of WOLEDs for the efficiency/color quality/brightness trade-off optimization that is necessary for pure white light of great commercial value.