Surface Reconstruction for Stable Monolithic All‐Inorganic Perovskite/Organic Tandem Solar Cells with over 21% Efficiency

Abstract

The construction of monolithic two‐terminal tandem solar cells (2T TSCs) offers the possibility of pursuing high power conversion efficiency (PCE) by overcoming the single‐junction Shockley–Queisser limit in photovoltaics. However, little attention is paid to simultaneously improve the stability by utilizing the complementary properties of various photoactive layers. Here, beyond the stacked photoactive layers featuring complementary absorption, all‐inorganic perovskite (CsPbI1.8Br1.2) is chosen as the photoactive layer of the front wide‐bandgap subcell for its intrinsic high thermal stability and ultraviolet (UV)‐filtering function to address the burn‐in and UV degradation of organic rear subcells. To realize their monolithic integration, the charge recombination efficiency in the interconnecting layer (ICL) between the two types of subcells is tentatively improved by surface reconstruction of all‐inorganic perovskite using trimethylammonium chloride. The repaired CsPbI1.8Br1.2 surface enables effective suppression of nonradiative recombination and facilitates hole transport, providing efficient charge recombination in the ICL in the 2T TSC. As a result, the all‐inorganic perovskite/organic 2T TSC delivers a promising PCE of 21.04%, accompanied by an ultrahigh open‐circuit voltage (Voc) of 2.05 V, which is nearly equal to the superposition of the respective Voc values of the subcells. More importantly, the 2T TSC simultaneously shows outstanding operational and UV stabilities.

Stoichiometric Dissolution of Defective CsPbI2Br Surfaces for Inorganic Solar Cells with 17.5% Efficiency

“…[11,12] Nevertheless, the Cs-based inorganic devices are still far from the Shockley-Queisser (SQ) efficiency limit because of the numerous intrinsic defects on the film surface that act as nonradiative recombination centers inducing additional voltage losses. [13,14] Several organic compounds, such as phenylethylammonium iodide, [15] methylammonium pyridine-2-carboxylic [16] and iodopentafluorobenzene, [17] have been utilized to passivate the ionic defects or the undercoordinated bonds due to associated intermolecular interactions on the perovskite surface [18] However, recent approaches have identified a defective region comprising disconnected nanocrystals or amorphous phases beneath the surface of perovskite polycrystalline films (approximately 0-50 nm), that cannot be resolved by regular surface passivation techniques. [19,20] Although mechanical polishing is a useful way to remove the defective nanostructured surface and ensures a long operational lifetime for PSCs, it is still hard to remove the defective surface uniformly by a few nanometers on large-area perovskite film, which renders the repeatability of device fabrication challenges.…”

Back-Contact Ionic Compound Engineering Boosting the Efficiency and Stability of Blade-Coated Perovskite Solar Cells

“…Nevertheless, SEM results clearly showed that the surface of the perovskite film became rough after HETACl treatment. Because the performance of PSCs is highly dependent on the microstructures of the perovskite films, this could result in poor reproducibility for cell efficiencies. , By contrast, perovskite films treated with BTACl deliver larger grains, as the average grain size is increased from 100 to 150 nm (Figure c). The increased grain size could be induced by Cl – , which heals the grain boundaries of the perovskite films as being widely reported. − In particular, the perovskite surface remains smooth after being treated by BTACl.…”

A Perspective on Perovskite Solar Cells: Emergence, Progress, and Commercialization

“…In addition, perovskites have been demonstrated as promising candidates in multi-junction cells due their easily tunable bandgap through constituents ( Al-Ashouri et al, 2020 ; Chen et al, 2021 ; Chen et al, 2022 ; Lin et al, 2022 ; Qin et al, 2022 ). The state-of-the-art perovskite-on-silicon tandem solar cell has achieved a PCE of 29.52% in Oxford PV on approximately 30 × 30 cm 2 device area ( Al-Ashouri et al, 2020 ).…”