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Triplet acceptors have been developed to construct high‐performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T1) are close to those of charge‐transfer states (3CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large π‐conjugated core and D‐A structure, were confirmed to be triplet materials, leading to high‐performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D‐A structures result in large spin–orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T1 is close to 3CT, facilitating the split of triplet exciton to free charges., Triplet materials are designed by introducing heavy atoms to enhance spin–orbit coupling or constructing donor and acceptor units with a twisted conformation to reduce ΔE ST. However, the twisted materials have not been applied in solar cells due to weak absorption and low charge‐transport mobilities. Now two nonplanar acceptors with large π‐conjugated core were constructed that achieved over 15 % efficiency.

The effect of low-temperature dynamic vacuum annealing (DVA) of sol–gel ZnO films on inverted polymer solar cells (IPSCs), which are composed of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PC61BM), was systematically investigated. The results show that IPSCs with low-temperature DVA-based ZnO films exhibit 15.9% enhancement within a power-conversion efficiency (PCE) of 4.01%, compared with IPSCs with conventional annealing-process-based ZnO films. The surface morphology measurement of ZnO films, light intensity dependent solar cell behaviors, and impedance spectroscopy of devices were investigated to study the performance of IPSCs. The dramatic enhancement of PCE was attributed to the improved surface morphology, optimized carrier transport characteristics, prolonged charge carrier lifetime, and reduced recombination rate. These results indicate that the low-temperature DVA process could be a promising method for producing high-quality ZnO films and high-performance IPSCs.

Methylammonium lead iodide (CH

Methylammonium lead iodide (CH3NH3PbI3), with the organic-inorganic hybrid perovskite (OIHP) structure, has gained tremendous research interest due to its excellent photo-electron conversion ability in the application of photovoltaics. Despite its solution processed polycrystalline thin film form in solar cells, the single crystalline counterpart may offer some incredibly novel optoelectronic functionalities. In this work, a sizable (>5 mm) and high quality CH3NH3PbI3 single crystal has been synthesized by the inverse temperature crystallization method, and a white-light photodetector of the structure glass/ITO/Ga/ CH3NH3PbI3/Au was fabricated. Overbroad photo-excitation intensities ranging from 0.1 mW/cm2 to 100 mW/cm2 using a sun-light simulator, the on-off ratio is tunable in a wide-range from 65 to 2250 at zero bias voltage. The responsivity (R) and detectivity (D*) are 36.2 mA/W and 2.68×1011 Jones respectively at a weak white-light intensity such as 0.1 mW/cm2. Both the photodetective parameters decrease with the increase of the illumination intensity. Based on impedance spectra obtained at working condition and light intensity dependent Jsc measurements, the surface trap-assist recombination may play a dominating role. The corresponding lifetime (τsurf) and resistance (Rsurf_trap) exhibit fast decays at higher illumination intensities. This fundamental study may pave the way for exploring the contribution of the surface trap-assist recombination in the CH3NH3PbI3 single crystal based photodetector. We believe it is applicable for integration in micro-photonics for sensitive and weak white-light photo-detection.