Kang Chen

Thermal degradation in perovskite solar cells is still an unsettled issue that limits its further development. In this study, 2-(1H-pyrazol-1-yl)pyridine is introduced into lead halide 3D perovskites, which allows 1D–3D hybrid perovskite materials to be obtained. The heterostructural 1D–3D perovskites are proved to be capable of remarkably prolonging the photoluminescence decay lifetime and suppressing charge carrier recombination in comparison to conventional 3D perovskites. The intrinsic properties of thermodynamically stable yet kinetically labile 1D materials allow the system to alleviate the lattice mismatch and passivate the interface traps of heterojunction region of 1D–3D hybrid perovskites that may occur during the crystal growth process. Importantly, the as-fabricated 1D–3D perovskite solar cells display a thermodynamic self-healing ability, which is induced through blocking the ion-migration channels of A-site ions by the flexible 1D perovskite with less densely close-packed structure. Particularly, the power conversion efficiency of as-fabricated unencapsulated 1D–3D perovskite solar cells is demonstrated to be reversible under temperature cycling (25–85 °C) at 55% relative humidity, which largely outperforms the pure 3D perovskite solar cell. The present study provides a facile approach to fabricate 1D–3D perovskite solar cells with high efficiency and long-term stability.

1D–3D hybrid perovskite is applied as absorber in a solar cell for the first time with remarkable thermodynamic self-healing capability. The power conversion efficiency of as-fabricated unencapsulated 1D–3D perovskite solar cells is demonstrated to be reversible under temperature cycling (25–85 °C) at 55% relative humidity, which largely outperforms the pure 3D perovskite solar cell.

The collection efficiency of photogenerated charges in polymer solar cells (PSCs) is strongly influenced by the built-in field (E_in) that develops across the photoactive materials. Here, by investigating the E_in-development regimes in PSCs by introducing two types of interlayers, electric dipole layers (EDLs) and charge transport layers (CTLs), the device architecture is optimized to result in a larger E_in. By incorporating a pair of EDLs on both sides of the photoactive layer, the E_in is modulated by shifting the vacuum energy at each metal–semiconductor interface, providing a larger E_in than that in conventional PSCs using typical CTLs, such as metal oxides and/or conducting polymers. These devices using paired EDLs exhibit an average PCE of 9.8%, which far surpasses the average PCE of ≈8.5% for paired CTLs.

Polymer solar cells with a new device architecture for reinforcing built-in electric field is demonstrated. A pair of strong electric dipole layers on both sides of the photoactive layer maximizes internal electric field in the operating state under short circuit condition, which permits an efficient “sweep out” of photo generated charges compared to those of typical charge transport layers.

Planar perovskite solar cells (PSCs) based on low-temperature-processed (LTP) SnO₂ have demonstrated excellent photovoltaic properties duo to the high electron mobility, wide bandgap, and suitable band energy alignment of LTP SnO₂. However, planar PSCs or mesoporous (mp) PSCs based on high-temperature-processed (HTP) SnO₂ show much degraded performance. Here, a new strategy with fully HTP Mg-doped quantum dot SnO₂ as blocking layer (bl) and a quite thin SnO₂ nanoparticle as mp layer are developed. The performances of both planar and mp PSCs has been greatly improved. The use of Mg-SnO₂ in planar PSCs yields a high-stabilized power conversion efficiency (PCE) of close to 17%. The champion of mp cells exhibits hysteresis free and stable performance with a high-stabilized PCE of 19.12%. The inclusion of thin mp SnO₂ in PSCs not only plays a role of an energy bridge, facilitating electrons transfer from perovskite to SnO₂ bl, but also enhances the contact area of SnO₂ with perovskite absorber. Impedance analysis suggests that the thin mp layer is an “active scaffold” selectively collecting electrons from perovskite and can eliminate hysteresis and effectively suppress recombination. This is an inspiring advance toward high-performance PSCs with HTP mp SnO₂.

A fully high-temperature (HT)-processed Mg-incorporated quantum dot (QD) SnO₂ blocking layer (bl)/mesoporous (mp) SnO₂ layer is used for the fabrication of perovskite solar cells (PSCs). Optimized fully HT mp SnO₂ PSCs can be achieved using an Mg-incorporated QD SnO₂ bl/100-nm-thick mp SnO₂ layer and its champion cell harvests a high stabilized power conversion efficiency of 19.2% with hysteresis free and stable performance.