This work provides an efficient way to facilitate both electron and hole extraction in the designated interfaces of perovskite solar cells. A record power conversion efficiency of 23.6% for mixed Sn–Pb perovskite solar cell devices is realized.

The toxicity of lead perovskite hampers the commercialization of perovskite-based photovoltaics. While tin perovskite is a promising alternative, the facile oxidation of tin(II) to tin(IV) causes a high density of defects, resulting in lower solar cell efficiencies. Here, we show that tin(0) nanoparticles in the precursor solution can scavenge tin(IV) impurities, and demonstrate that this treatment leads to effectively tin(IV)-free perovskite films with strong photoluminescence and prolonged decay lifetimes. These nanoparticles are generated by the selective reaction of a dihydropyrazine derivative with the tin(II) fluoride additive already present in the precursor solution. Using this nanoparticle treatment, the power conversion efficiency of tin-based solar cells reaches 11.5%, with an open-circuit voltage of 0.76 V. Our nanoparticle treatment is a simple and broadly effective method that improves the purity and electrical performance of tin perovskite films.

Maltol, a metal binding agent, effectively passivates defects on the surface of mixed lead–tin perovskite films. The carrier lifetimes of the resultant perovskite films are over 7 μs. The solar cell devices exhibit efficiencies of up to 21.4%.

Carrier extraction is a key issue which limits the efficiency of perovskite solar cells. In this work, carrier extraction is improved by modifying the perovskite layers with a combination of ethylenediammonium diiodide post-treatment and glycine hydrochloride additive. Ethylenediammonium dications primarily affect the top surface of the perovskite films, while glycinium cations preferentially accumulate at the bottom region. The top and bottom interface modifications improve the crystallinity of the perovskite films and lower the density of electrical traps via surface passivation effects, resulting in long charge carrier lifetimes. The orientated aggregation of the ethylenediammonium and glycinium cations at the charge collection interfaces result in the formation of surface dipoles, which facilitate charge extraction. The performance of the treated solar cell devices also increases. The fill factor rose to 0.82, and the power conversion efficiency reaches 23.6% (23.1% certified). The open circuit voltage reaches 0.91 V, just 0.06 V below the Shockley–Queisser limit. The unencapsulated devices also show improved stability under AM 1.5G, retaining over 80% of the initial efficiency after 200 h continuous operation in inert atmosphere. Our strategy is also successfully applied to centimeter-scale devices, with efficiencies up to 21.0%.

Organic semiconducting materials that are optically transparent in the near-ultraviolet (NUV) region from 300 to 400 nm are needed for advanced perovskite devices such as bifacial semitransparent and tandem solar cells. In this study, three organic semiconducting materials, HND-NAr 2 , HND-DTP, and HND-Cbz, were designed and synthesized by introducing bis(4methoxyphenyl)amine, dithieno[3,2-b:2′,3′-d]pyrrole, and carbazole, respectively, into the head position of partially oxygenbridged triphenylamine skeletons. The combination of oxygenbridged triphenylamine and an electron-donating group at the head position suppresses the π−π* transition, leading to weak absorption in the NUV region. Thin films of the materials can be fabricated by both solution and vacuum-deposition processes, and applied as the hole-transporting material (HTM) in perovskite solar cells (PSCs). The power conversion efficiency (PCE) of conventional devices with these HTMs was 13.7% (HND-Cbz), 15.0% (HND-DTP), and 17.2% (HND-NAr 2 ). When used in bifacial semitransparent PSCs, the incident photon-to-current conversion efficiency (IPCE) at 400 nm was 41% (HND-NAr 2 ), 45% (HND-Cbz), and 46% (HND-DTP), significantly higher than that of a reference using 2,2′,7,7′-tetrakis(N,N-di-p-metoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) as the HTM (14%) as a result of the improved optical transmission through the HTM.