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Silicon‐based tandem solar cells are regarded as one of the most feasible ways to break the single‐junction Shockley–Queisser limit efficiency and further reduce the cost of solar electricity. Recently, wide‐bandgap (≈1.7 eV) perovskite solar cells have drawn intense research interest as the top cell for Si‐based tandem devices. Despite significant progress in device efficiency, the unsatisfactory stability of perovskites is still a huge concern. Besides halide perovskites, there are many inorganic semiconductors worthy of investigation. It is believed that cadmium selenide, a binary compound enjoying outstanding optoelectronic properties, high stability, and low cost, is very promising as the top cell for Si‐based tandem devices. Herein, the CdSe thin‐film solar cells that have been neglected for 3 decades are revisited. Using rapid thermal evaporation, high‐quality CdSe thin films with large grain size, high‐photoluminescence, small Stokes shift, and intrinsic n‐type conductivity are obtained. Furthermore, CdSe solar cells are redesigned and a champion efficiency of 6.00% is achieved. Through in‐depth analysis, it is identified that bulk and interface defects limit the open‐circuit voltage and hence device performance. This work highlights the great potential of CdSe solar cells as top cells for Si‐based tandem devices. [ABSTRACT FROM AUTHOR]

Solar cells are promising devices for converting sunlight into electrical energy. Tandem solar devices, which combine multiple sub cells with complementary absorption spectra, offer a potential strategy to enhance the overall power conversion efficiency (PCE). In this work, the design and performance of organic/CIGS tandem solar devices are investigated. The initial tandem cell comprises two sub cells, namely an organic-based PM6:m-DTC-2 F top cell and CIGS bottom cell. The organic and CIGS cells show a PCE of 12.20% and 20.10%, respectively, where the initial results are based on calibrated cells reproduced from experimental studies. Accordingly, the initial tandem PM6:m-DTC-2 F/CIGS cell shows a PCE of 22.75%. The study focuses on optimizing the PCE via different approaches. Firstly, through the exploration of different hole transport layers (HTLs) of the front cell. Secondly, by investigating the matched current condition between the front and rear cells. Moreover, the doping effect of the CIGS film is investigated. Finally, optimization of the defect concentrations in the absorbers is introduced. These optimizations result in open circuit voltage (V oc) of 1.89 V with short circuit current (J sc) of 17.55 mA/cm2, and a fill factor (FF) of 82.79%. Consequently, the PCE of the optimized tandem cell is further enhanced to 27.46%. Further, the stability of the proposed tandem cell is evaluated under varying temperatures, and its composition of flexible materials makes it a promising candidate for wearable applications. [ABSTRACT FROM AUTHOR]

Here, highly efficient and stable monolithic (2‐terminal (2T)) perovskite/PbS quantum dots (QDs) tandem solar cells are reported, where the perovskite solar cell (PSC) acts as the front cell and the PbS QDs device with a narrow bandgap acts as the back cell. Specifically, ZnO nanowires (NWs) passivated by SnO2 are employed as an electron transporting layer for PSC front cell, leading to a single cell PSC with maximum power conversion efficiency (PCE) of 22.15%, which is the most efficient NWs‐based PSCs in the literature. By surface passivation of PbS QDs by CdCl2, QD devices with an improved open‐circuit voltage and a PCE of 8.46% (bandgap of QDs: 0.92 eV) are achieved. After proper optimization, 2T and 4T tandem devices with stabilized PCEs of 17.1% and 21.1% are achieved, respectively, where the 2T tandem device shows the highest efficiency reported in the literature for this design. Interestingly, the 2T tandem cell shows excellent operational stability over 500 h under continuous illumination with only 6% PCE loss. More importantly, this device without any packaging depicts impressive ambient stability (almost no change) after 70 days in an environment with controlled 65% relative humidity, thanks to the superior air stability of the PbS QDs. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) have experienced a rapid progress in terms of efficiency in both single and tandem structures. Herein, two‐terminal (2T) tandem design is fabricated using PV2000:PCBM (1.65 eV) and PM6:Y6 (1.3 eV) blends as bottom and top cells, respectively. The role of transporting and recombination layers on photovoltaic (PV) parameters is studied. The impedance and transmittance results indicate that using SnO2 nanocrystals (NCs) as an electron transporting layer (ETL) in both subcells, the fill factor (FF) and the open circuit voltage (VOC) of the tandem device are increased drastically, mainly due to the lower resistance of the SnO2 layer and its higher transmittance as compared with the ZnO ETL. Moreover, it is found that the VOC and FF losses are reduced using poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/Ag (1 nm)/SnO2 NCs as a recombination layer in the tandem design. After proper optimization, a tandem OSC with a VOC of 1.61 V and an efficiency of 14.4% is achieved, which shows great operational stability as well. In addition, the current match and efficiency of the tandem device are increased up to 12.94 mA cm−2 and 15.2%, respectively, by applying a nanotextured anti‐reflection layer on the back of the device. [ABSTRACT FROM AUTHOR]