All-polymer solar cells have shown great potential as flexible and portable power generators. These devices should offer good mechanical endurance with high power-conversion efficiency for viability in commercial applications. In this work, we develop highly efficient and mechanically robust all-polymer solar cells that are based on the PBDTTTPD polymer donor and the P(NDI2HD-T) polymer acceptor. These systems exhibit high power-conversion efficiency of 6.64%. Also, the proposed all-polymer solar cells have even better performance than the control polymer-fullerene devices with phenyl-C₆₁-butyric acid methyl ester (PCBM) as the electron acceptor (6.12%). More importantly, our all-polymer solar cells exhibit dramatically enhanced strength and flexibility compared with polymer/PCBM devices, with 60- and 470-fold improvements in elongation at break and toughness, respectively. The superior mechanical properties of all-polymer solar cells afford greater tolerance to severe deformations than conventional polymer-fullerene solar cells, making them much better candidates for applications in flexible and portable devices.

A facile and low-temperature process to prepare planar perovskite solar cells (PSCs) has led to considerable progress in flexible solar cells toward high throughput production based on a roll-to-roll process. However, the performance of planar PSCs is still lower than that of mesoscopic PSCs using a high temperature process. Here, we report a new concept of a low temperature processed porous planar electron transport layer (ETL) inspired by a mesoporous structure for improving the performance of flexible devices. The structurally and energetically designed porous planar ETL induced the formation of a high quality perovskite and a preferred band alignment, resulting in improved charge collection efficiency in a fabricated device. Through the porous planar ETL, we achieved a power conversion efficiency (PCE) of 20.7% with a certified efficiency of 19.9% on a flexible substrate, which is the highest PCE reported to date. In addition, for the first time, we succeed in fabricating a large area flexible module with the porous planar ETL, demonstrating a PCE of 15.5%, 12.9% and 11.8% on an aperture area of 100 cm², 225 cm² and 400 cm², respectively. We believe that this strategy will pave a new way for realizing highly efficient flexible PSCs.

Developing polymer solar cells (PSCs) with high photovoltaic performance and mechanical robustness is one of the most urgent tasks to ensure their operational reliability and applicability in wearable devices. However, it remains challenging to enhance their mechanical properties without compromising the electrical properties of high-performance active materials. Here, we develop a series of novel polymer donors (P_Ds), with which highly efficient PSCs having remarkable mechanical reliability are demonstrated. By interposing a controlled amount of 1,10-di(thiophen-2-yl)decane flexible spacer (FS) into a PM6 backbone, we are able to significantly enhance the intermixing of the new P_Ds with a small molecule acceptor (Y7), affording sufficient pathways for efficient charge percolation and mechanical stress dissipation. As a result, PSCs based on the P_D containing 5 mol% FS units and Y7 exhibit a high power conversion efficiency (PCE) of 17% with a crack onset strain (COS) of 12% and a cohesive fracture energy (G_c) of 2.1 J m⁻², significantly outperforming reference PM6-based devices (PCE = 15%, COS = 2% and G_c = 1.0 J m⁻²). Both the photovoltaic performance and mechanical robustness of these PSCs are among the best values reported to date. The rational design of the P_Ds demonstrated here presents a highly promising strategy to address the mechanical properties of SMA-based solar cells and their viable application in flexible/stretchable electronics.