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Although significant advancements have been achieved in lead-tin (Pb-Sn) alloyed perovskite solar cells (PSCs), their power conversion efficiency (PCE) remains inferior to that of their Pb-based counterparts, primarily due to higher open-circuit voltage ( V oc ) losses and lower fill factors (FFs). Herein, we report both perovskite top and bottom interfacial improvements by incorporating a facile fluorophenylethylammonium iodide (p-FPEAI)/ethyl acetate (EA) solution during the film crystal growth. Based on the analysis of perovskite crystallization, film growth, and strain relaxation, the mechanisms behind these interfacial improvements have been well understood. Furthermore, p-FPEAI could reduce the defect density and nonradiative recombination losses, thus attributing to the improved V oc and FF. Finally, the treated device achieved a PCE of 20.14% with a V oc of up to 0.84 V, which is among the highest reported values so far for Pb-Sn alloyed PSCs without additional precursor additives. In addition, the unencapsulated p-FPEAI-treated device maintained its initial efficiency of approximately 92% after being kept in a nitrogen atmosphere for 1 month, in contrast to the control device which retained only 30% of its initial value. Our findings provide a comprehension for understanding the effect of bulky cations as antisolvents on fabricating highly efficient Pb-Sn alloyed perovskite solar cells.

Perovskite solar cells (PSCs) based on sputtered nickel oxide (NiO x ) hole transport layer have emerged as promising configuration due to their good stability, cost-effectiveness, and scalability. However, the adverse chemical redox reaction at the NiO x /perovskite interface remains an ever-present problem that has not yet been well solved. To address this issue before, the problems that cation deprotonation and iodide oxidation that occurred in precursor solution easily result in the interfacial chemical reaction should be prevented. Hence, we report an efficient strategy to simultaneously suppress the interfacial reaction and stabilize the precursor solution by incorporating a reducing and weakly acidic stabilizer, l-ascorbic acid (l-AA). l-AA can reduce I 2 generated in the precursor solution and during the interfacial reaction to I - . Furthermore, the protons ionized by adjacent enol hydroxyl groups in l-AA effectively impede the deprotonation of organic cations in the precursor solution as well as at the NiO x /perovskite interface resulting from the chemical reaction. Attributing to the improved crystallization of the perovskite film and the suppression of the interfacial reaction by l-AA, the inverted PSC based on such good light absorber achieves an impressive power conversion efficiency (PCE) of 22.72% along with a high open-circuit voltage of 1.19 V. Notably, further introducing l-AA into the large-area solar modules by the slot-die coating method in air enables a remarkable PCE of 19.17%, which reaches one of the highest PCEs reported for inverted perovskite solar modules (PSMs) (active area >50 cm 2 ) to date. l-AA located at the buried interface also forms a barrier layer that can prevent undesirable chemical reactions at the NiO x /perovskite interface, significantly enhancing the device stability of solar cells and PSMs. These findings in our work provide important guidance for improving the NiO x /perovskite interface and the fabrication of highly efficient, low-cost, and large-area PSMs.

Despite two-dimensional (2D) Ruddlesden-Popper-phase layered perovskites (RPLPs) exhibiting excellent environmental stability, most solar cells based on 2D RPLP films are fabricated in a controlled inert atmosphere. Meanwhile, the poor charge transport of 2D RPLP films owing to the unfavorable phase arrangement and defects limits the efficiency of 2D RPLP solar cells. Here, we fabricate high-efficiency 2D RPLP solar cells in ambient air assisted by a zwitterion (ZW) additive. We show that the ZW additive suppresses the formation of the bottom 2D phases ( n ≤ 2) and the top 3D-like phases in 2D RPLP films. These 2D phases usually grow parallel to the substrate and act as trap sites that inhibit charge transport in the vertical direction. The 3D-like phases, on the other hand, aggravate the long-term stability due to the intrinsic instability of MA + cations. With improved phase distribution, crystal orientation, and reduced trap states in 2D RPLP films, efficient charge transport is obtained. Finally, a record-high open-circuit voltage ( V oc ) of 1.19 V and a power conversion efficiency of 17.04% with an enhanced stability are achieved for (BA 0.9 PEA 0.1 ) 2 MA 3 Pb 4 I 13 -based ( n = 4) solar cells fabricated under high humidity (∼65% RH).

The inorganic CsPbI 3 perovskite has attracted tremendous attention in the photovoltaic fields for its chemical stability and suitable band gap. Generally, CsPbI 3 solar cells with decent performances adopted high annealing temperature to form high-quality black-phase perovskite films. The high-temperature process hinders its practical application and further development. Hence, fabricating stable black-phase CsPbI 3 at low temperature is imperative and necessary. In this work, a new additive p -xylilenediamine bromide (PhDMADBr) is reported to facilitate the synthesis of solution-processed, high-quality, and stable γ-CsPbI 3 films at a surprisingly low temperature of 60 °C. The additive with an appropriate content can effectively improve both the film morphology and crystallinity of γ-CsPbI 3 perovskite films. PhDMADBr anchors to the perovskite surface or grain boundaries as a protection through hydrogen bonding between its ammonium cations and CsPbI 3 . In addition, the Br element introduced by the additive passivates I - vacancies in perovskite films, resulting in the improvement of both phase stability and devices' performance. Finally, the PSCs based on the modified γ-CsPbI 3 perovskite film achieve a champion efficiency of 12.71%. Moreover, the device retains 85% of its original efficiency after being kept for 1000 h.

An ideal photodetector must exhibit a fast and wide tunable spectral response, be highly responsive, have low power consumption, and have a facile fabrication process. In this work, a self-powered photodetector with a graphene electrode and a perovskite photoactive layer is assembled for the first time. The graphene electrode is prepared using a solution transfer process, and the perovskite layer is prepared using a solution coating process, which makes the device low cost. Graphene can form a Schottky junction with TiO 2 to efficiently separate/transport photogenerated excitons at the graphene/perovskite interface. Unlike the conventional photovoltaic structure, in this photodetector, both photogenerated electrons and holes are transported along the same direction to graphene, and electrons tunneled into TiO 2 are collected by the cathode and holes transported by graphene are collected by the anode; therefore, the photodetector is self-powered. The photodetector has a broad range of detection, from 260 to 900 nm, an ultrahigh on-off ratio of 4 × 10 6 , rapid response to light on-off (<5 ms), and a high level of detection of ∼10 11 Jones. The high performance is primarily due to the unique charge-transport property of graphene and strong light absorption properties of perovskite. This work suggests a new method for the production of self-powered photodetectors with high performance and low power consumption on a large scale.