Microcavity is an efficient approach to manufacture colorful semitransparent organic solar cells (ST-OSCs) with high color purity by tailoring the transmission spectrum to narrow peaks. However, in this type of colorful semitransparent devices, high power conversion efficiency (PCE) and high peak transmittance are not yet simultaneously achieved. This paper proposes a new type of microcavity structure to achieve colorful ST-OSCs with both high PCE and high peak transmittance, in which a hybrid Au/Ag electrode is used as a mirror and WO3 is used as a spacer layer. First, it is demonstrated that the hybrid Au/Ag electrode mirror brings about an improvement of 7.7 and 5.5% for PCE and peak transmittance, respectively, when compared with those of the reference devices using the Ag electrode mirror. Specifically, the PCE of the optimized devices reaches the satisfactory value of over 9%, and the peak transmittance is over 25%. This value of PCE is the highest one reported so far for the microcavity-based ST-OSCs with the same peak transmittance. Second, it is demonstrated that the second-order resonance of the microcavity can be used to improve the color purity of green ST-OSCs by narrowing the transmission peak, and the combination of the second-order and third-order resonance can be used to construct colorful ST-OSCs with mixed colors. Thus, a novel approach is developed to tune the color of ST-OSCs, which is based on high-order resonance modes of the microcavity.

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Hot electron photodetectors based on a planar structure of metal-insulator /semiconductor-metal (MIM/MSM) have attracted much attention due to the easy and cheap fabrication process and the possibility of detecting light with energy lower than the semiconductor band gap. For this type of device, however, hot electron photocurrent is restricted by the trade-off between the light absorption and the internal quantum efficiency (IQE) since high absorption usually occurs within thick metals and the IQE in this case is usually low. The trade-off is circumvented in this paper by proposing a new type of hot electron photodetector based on planar MIM structure and coupled dual Tamm plasmons (TPs), which has a structure of one-dimensional photonic crystals (1DPCs)/Au/TiO2/Au/1DPCs. The coupled modes of the dual TPs at the two 1DPCs/Au interfaces can lead to a high absorption of 98% in a 5 nm-thick Au layer. As a result, the responsivity of the conventional device with two Schottky junctions in series configuration reaches a high value of 9.78 mA/W at the wavelength of 800 nm. To further improve the device performance, devices with four Schottky junctions in parallel configuration are proposed to circumvent the hot electrons loss at the interface of the Au layer and the first TiO2 layer of the 1DPCs. Correspondingly, the hot electrons photocurrent doubles and reaches a higher value of 21.87 mA/W. Moreover, the bandwidth of the responsivity is less than 0.4 nm, the narrowest one when compared with that for the hot electron photodetectors reported so far in the published papers.

Plasmonic harvesting of hot carriers (HCs) in metal−semiconductor (M−S) junctions has stimulated intensive research activities for sub-bandgap photodetection, in particular the development of silicon-based infrared photodetectors. Here, a copper−silicon heterojunction was investigated both theoretically and experimentally in comparison to the commonly used gold− silicon ones. A 1-order-of-magnitude higher responsivity and a longer cutoff wavelength over 2000 nm were observed in experiments in the sub-bandgap wavelength range of silicon with a copper−silicon junction. A phenomenological model was developed to analyze the dynamic processes of HCs and attributed the advanced photodetection performance of copper−silicon devices to the relatively higher electron density of state above the Fermi level and the higher ejection probability. Such a complementary metal−oxide− semiconductor-compatible and low-cost HC photodetection platform shows promising potential in silicon-based optoelectronic applications.