The combination of hybrid perovskite and Cu(In,Ga)Se (CIGS) has the potential for realizing high-efficiency thin-film tandem solar cells because of the complementary tunable bandgaps and excellent photovoltaic properties of these materials. In tandem solar device architectures, the interconnecting layer plays a critical role in determining the overall cell performance, requiring both an effective electrical connection and high optical transparency. We used nanoscale interface engineering of the CIGS surface and a heavily doped poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) hole transport layer between the subcells that preserves open-circuit voltage and enhances both the fill factor and short-circuit current. A monolithic perovskite/CIGS tandem solar cell achieved a 22.43% efficiency, and unencapsulated devices under ambient conditions maintained 88% of their initial efficiency after 500 hours of aging under continuous 1-sun illumination.

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The device characteristics of polymer solar cells with cesium carbonate (Cs2CO3) as an electron-injection interlayer have been investigated. It is found that the insertion of Cs2CO3 at the cathode interface improves the device power conversion efficiency from 2.3% to 3.1%. In order to further understand the mechanism, the interfacial interaction between the active organic layer and the cathode was studied by x-ray photoemission spectroscopy (XPS). The results of XPS measurement indicate the fact that a portion of electrons transfer from the interlayer into the organic layer, resulting in n-type doping. The n-doping effect enhances the efficiency of electron injection and collection. Further, the maximum open-circuit voltage (Voc) was determined from its temperature dependence. For the device with Cs2CO3, the maximum Voc is extremely close to the corresponding value of the energy difference between the highest occupied molecular orbital of the electron donor and the lowest unoccupied molecular orbital of the electron acceptor, suggesting a better Ohmic contact. All evidences indicated that Cs2CO3 is a promising candidate as an interlayer to improve the device performance.

Increasing demand of wireless devices contributes to radiofrequency (RF) congestion. Light Fidelity (LiFi) promises to be an interesting alternative by using the visible part of the electromagnetic spectrum instead of the RF part as nearly all existing wireless transmission systems do. A basic LiFi system is composed of one intensity-controlled lightemitting diode (LED) and one receiver device sensitive to very high-frequency (thus invisible to human sight) modulations of the luminous intensity. In most cases, the photoreceptor is a silicon photodiode of PIN (P-type intrinsic N-type) or APD (Avalanche photodiode) conception. Recently, a few studies suggest that photovoltaic (PV) modules could be used to implement outdoor LiFi transmissions, i.e., under direct sunlight exposure. In this paper, we propose to compare the behavior of a PV module and a commercial APD-based photodetector (without any optical lens or colored filter) for experimental LiFi transmissions on both indoor and outdoor conditions. The performance of the two solutions is quantified in terms of various frequency responses like attenuation, signal-to-noise ratio, or bit-error rate. The results show that, while the photodiode exhibits very good performance in indoor conditions, its frequency response is rapidly deteriorating when a sunlight exposure of more than 200W/m 2 is superimposed over the LiFi signal. We demonstrate that a PV module in Voc (open-circuit voltage) condition still operates a LiFi transmission under additional solar illumination.