• Energy Research

Three-dimensional/two-dimensional (3D/2D) heterojunctions in perovskite solar cells exhibit excellent optoelectronic properties and enhanced stability under mild ageing conditions.

Using a fully automated device acceleration platform (DAP) to systematically optimize air-processed parameters and establish a standard operation procedure (SOP) for preparing high-performance perovskite solar cells under ambient air.

AbstractA nonconjugated, alcohol‐soluble zwitterionic polymer, poly(sulfobetaine methacrylate) (denoted by PSBMA), is employed as cathode interfacial layer (CIL) in polymer solar cells (PSCs) based on PTB7‐Th:PC71BM. Compared with the control device without CIL, PSCs with PSBMA CILs show significant enhancement on the resulting performance, and the highest power conversion efficiency (PCE) of 8.27% is achieved. Under parallel conditions, PSCs with PSBMA as CIL show comparable performance than those with widely used poly[(9,9‐bis(30‐(N,N‐dimethylamino)propyl)‐2,7‐fluorene)‐alt‐2,7‐(9,9‐ioctylfluorene)] as CIL. The polar groups of PSBMA not only provide a solvent orthogonal solubility in the process of preparation of the devices but also lead to interfacial dipole to the electrode, which promises a better energy level alignment. In addition, PSBMA‐based devices show better abilities of hole blocking. These results indicate that the zwitterionic polymer PSBMA should be a promising CIL in PSC‐based narrow‐bandgap polymers.

A molecular hole transport material retards the iodine migration and delivers high stability in a harsh 85 °C MPP test.

Fully printed carbon-based flexible perovskite module with an efficiency of 11.6%.

Lead–tin (Pb/Sn) mixed perovskites are considered as promising photovoltaic materials owing to their adjustable bandgap and excellent optoelectronic properties. The low‐bandgap perovskite solar cells (PSCs) based on lead–tin mixed perovskites play a critical role in the overall performance of perovskite‐based tandem devices. Nevertheless, the current record efficiencies for Pb/Sn PSCs are mostly reported in devices with p–i–n configuration rather than n–i–p, which restricts the further development of conventional perovskite‐based tandem solar cells. Herein, this work systematically investigates the influence of the interlayers on the performance of low‐bandgap PSCs by analyzing the energy losses in both n–i–p and p–i–n devices. Quasi‐Fermi level splitting (QFLS) analysis of pristine films and films covering charge extraction layers reveals that the electron transport layer/perovskite interface is dominating the VOC losses. A joint experimental–simulative approach quantitatively determines the interface defect density to be more than one order in magnitude larger for the n–i–p architecture. Among the polymeric hole transport layers investigated for n–i–p devices, poly(3‐hexylthiophen‐2,5‐diyl) (P3HT) exhibits the most favorable energy‐level alignment to Pb/Sn perovskites. These results clarify the nature of VOC losses in Pb/Sn perovskites and highlight the necessity to develop electron extraction layers with a significantly reduced interface defect density.

AbstractAlmost all highly efficient perovskite solar cells (PVSCs) with power conversion efficiencies (PCEs) of greater than 22% currently contain the thermally unstable methylammonium (MA) molecule. MA‐free perovskites are an intrinsically more stable optoelectronic material for use in solar cells but compromise the performance of PVSCs with relatively large energy loss. Here, the open‐circuit voltage (Voc) deficit is circumvented by the incorporation of β‐guanidinopropionic acid (β‐GUA) molecules into an MA‐free bulk perovskite, which facilitates the formation of quasi‐2D structure with face‐on orientation. The 2D/3D hybrid perovskites embed at the grain boundaries of the 3D bulk perovskites and are distributed through half the thickness of the film, which effectively passivates defects and minimizes energy loss of the PVSCs through reduced charge recombination rates and enhanced charge extraction efficiencies. A PCE of 22.2% (certified efficiency of 21.5%) is achieved and the operational stability of the MA‐free PVSCs is improved.