Suppressing trap states and localized electronic states in the forbidden gap of semiconductors as either active layers or contacts is critical to the enhancement of optoelectronic device performance, such as for solar cells, ultrafast photodetectors, field-effect transistors, as well as other optoelectronic applications. In this study, we demonstrate that Lewis bases-passivated metal oxide n-type contacts can effectively improve the performance of organic solar cells (OSCs). OSCs with triethanolamine-passivated ZnO show a two orders of magnitude lower trap density, and thus a higher electron mobility, and three times longer charge carrier recombination lifetime, relative to the devices based on as-cast ZnO. Passivated ZnO universally improves the power conversion efficiency (PCE) of OSCs based on varied active layers. P3HT:PC71BM-based solar cells with passivated-ZnO yield 86% PCE enhancement relative to the control devices based on as-cast ZnO, and PM6:Y6-based devices with passivated-ZnO exhibit PCEs up to 15.61%. Furthermore, light stability of OSCs with passivated-ZnO has also been improved along with enhanced device efficiency. A Lewis base is also efficient to passivate SnO x contact for solar cells. This study highlights the importance of defect passivation on contact layers for improvement of the efficiency and stability of OSCs and also provides one facile and effective passivation strategy.

Comparing to 0 and 1 based binary systems, the organic ternary data-storage systems that record data as 0, 1 and 2 can hold much more data in a given amount...

Selective spectral response photodetectors (PDs) capable of accurately capturing the color of images have broad applications in industry and academia. Here, we demonstrate filter-free, wavelength-selective detection organic photodetectors (OPDs) with two distinct response ranges and having the planar bilayer heterojunction device structure by employing either a (semi-)­transparent anode or a cathode as the incident light window. The resultant OPDs exhibit a responsivity of 51 mA W–1 in the range 300–650 nm and 11 mA W–1 in the range 650–850 nm under top illumination condition. Similarly, the devices show a responsivity of 2 mA W–1 for the short-wavelength region and 131 mA W–1 for the long-wavelength region when under bottom illumination condition, indicating a high responsivity ratio that meets the requirements for selective detection. Hence, our individual device not only works in either visible or NIR range but also provides narrowband detection with spectral widths down to 100 nm in the NIR range. The working mechanism of spectral selectivity is identified through quantitative analysis of the external quantum efficiency (EQE) spectra using optical modeling when compared to the OPDs with bulk heterojunction structure, thus clarifying the general validity of the device design concept. Finally, our OPDs can demultiplex intermixed optical signals from the light-communication system successfully. Our results should inspire new studies on the device design concept and new applications of OPDs.

The previously proposed “charge-trap” mechanism guided us to design numbers of ternary samll-molecules and to construct the “structure-property” relationship. However, there are still a few molecules that cannot reflect the...

The influence of the absence of a π-conjugated polymer-based charge-blocking layer (CBL) or interlayer between the photoactive layer/electrode interface in organic photodetectors (OPDs) is investigated. As compared to devices with a chargeblocking layer, OPDs with a metal/photoactive layer/metal sandwich structure exhibit similar external quantum efficiency but lower dark current density hence a higher specific detectivity (D*). The decrease in dark current density in devices without a CBL can be attributed to the elimination of additional trap states in the CBL, provided that a large charge injection barrier is maintained at the metal/active layer interface. In a device with the CBL, a clear dependence between the density of trap states (tDOS) and the magnitude of dark current density is verified. As such, suppressing undesired injection and trap-induced leakage current may cancel each other out in the device with a CBL. By evaluating the trap-induced leakage of current, we proposed that the key to obtain high specific detectivity in OPDs is to use a charge-blocking layer with low trap density or to use a CBL-free device structure.