The performance of perovskite solar cells with inverted polarity ( p-i-n ) is still limited by recombination at their electron extraction interface, which also lowers the power conversion efficiency (PCE) of p-i-n perovskite-silicon tandem solar cells. A ~1 nm thick MgF x interlayer at the perovskite/C 60 interface through thermal evaporation favorably adjusts the surface energy of the perovskite layer, facilitating efficient electron extraction, and displaces C 60 from the perovskite surface to mitigate nonradiative recombination. These effects enable a champion V oc of 1.92 volts, an improved fill factor of 80.7%, and an independently certified stabilized PCE of 29.3% for a ~1 cm 2 monolithic perovskite-silicon tandem solar cell. The tandem retained ~95% of its initial performance following damp-heat testing (85 Celsius at 85% relative humidity) for > 1000 hours.

Chalcogenide-based quantum dots are useful for the application of memory-switching devices because of the control in the trap states in the materials. The control in the trap states can be achieved using a hot-injection colloidal synthesis method that produces temperature-dependent size-variable quantum dots. In addition to this, formation of a nanoscale heterostructure with an insulating material adds to the charge-trapped switching mechanism. Here, we have shown that the colloidal monodispersed CdSe quantum dots and poly(4-vinylpyridine) (PVP) formed a nanoscale heterostructure between themselves when taken in a suitable ratio to fabricate a device. This heterostructure helps realize memory-switching in the device with a maximum on−off current ratio of 10 5 . The switching in the device is mainly due to the trap states in the CdSe quantum dots. The conduction in the off state is due to thermal charge injection and space charge injection conduction and in the on state, due to the Ohmic conduction mechanism.

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Metal halide perovskite solar cells hold great promise as an efficient and cost-effective photovoltaic technology. However, carrier recombination at their contacts impedes progress toward this goal. In this study, considering the archetypical MAPbI 3 perovskite and Au as a model electrode, we employ first-principles calculations to show how the mere presence of a metal near the perovskite induces in-gap states that may impair electronically this contact because of carrier recombination and Fermi level pinning. The states are not associated with any defect. We then investigate the suppression of the contact-induced gap states by introducing various passivation molecules to displace the metal from the perovskite surface. Our results highlight from a fundamental perspective the importance of contact displacement and passivation for efficient perovskite solar cells, thereby elucidating further the role of thin molecular interlayers in experimental devices. The elimination of contact-induced gap states can greatly aid perovskite solar cells in fulfilling their promise as a future mainstream source of renewable electricity.