Stretchable Perovskite Solar Cells with Recoverable Performance

Abstract

Perovskite solar cells (PSCs) are a promising photovoltaic technology for stretchable applications because of their flexible, light‐weight, and low‐cost characteristics. However, the fragility of crystals and poor crystallinity of perovskite on stretchable substrates results in performance loss. In fact, grain boundary defects are the “Achilles’ heel” of optoelectronic and mechanical stability. We incorporate a self‐healing polyurethane (s‐PU) with dynamic oxime–carbamate bonds as a scaffold into the perovskite films, which simultaneously enhances crystallinity and passivates the grain boundary of the perovskite films. The stretchable PSCs with s‐PU deliver a stabilized efficiency of 19.15 % with negligible hysteresis, which is comparable to the performance on rigid substrates. The PSCs can maintain over 90 % of their initial efficiency after 3000 hours in air because of their self‐encapsulating structure. Importantly, the self‐healing function of the s‐PU scaffold was verified in situ. The s‐PU can release mechanical stress and repair cracks at the grain boundary on multiple levels. The devices recover 88 % of their original efficiency after 1000 cycles at 20 % stretch. We believe that this ingenious growth strategy for crystalline semiconductors will facilitate development of flexible and stretchable electronics.

Role and Contribution of Polymeric Additives in Perovskite Solar Cells: Crystal Growth Templates and Grain Boundary Passivators

“…Meng et al incorporated a self‐healing polyurethane(s‐PU) exhibiting dynamic oxime—carbamate bonds as a scaffold into perovskite films and simultaneously enhanced the crystallinity and passivated the GB of the perovskite films. [ 27 ] The stretchable PSCs fabricated with s‐PU delivered a stabilized efficiency of 19.15% and negligible hysteresis, comparable with the device performance obtained for rigid substrates. These PSCs maintained over 90% of their self‐encapsulating structure.…”

“…The mechanical properties (characterized by the Young's modulus) of PSC polymeric additives have become increasingly important with the emergence of flexible applications and self‐healing PSCs. [ 8,26–28 ] When polymeric additives settle between perovskite crystal grains, the additives hold the grains together by crosslinking. In flexible PSCs, external forces applied during bending or folding pull the grains apart.…”

Stretchable ITO‐Free Organic Solar Cells with Intrinsic Anti‐Reflection Substrate for High‐Efficiency Outdoor and Indoor Energy Harvesting

“…In this case, replacing the top metal with other electrodes, such as Ag NWs or PEDOT:PSS, would be an ideal method to improve the mechanical properties, especially the stretch stability. [ 75–78 ]…”

Moisture‐Triggered Self‐Healing Flexible Perovskite Photodetectors with Excellent Mechanical Stability

“…[30][31][32][33][34] To resolve these critical issues, the concept of self-healing has also been applied to flexible perovskite devices. [35,36] Selfhealing polymers can act as encapsulation layers or flexible substrates, which only prevent external air moisture while cracks inside perovskite films still exist and block carrier transport. In addition, it is difficult to endow the ABX 3 crystal structure of perovskite with special chemical bonds (such as H-bonds) to trigger the capability of self-healing.…”

“…To address this challenge, Chen et al creatively utilized polyurethanes (PU) to provide a micro-self-healing framework for perovskite crystals without damaging its power conversion efficiency and cracks caused by stretching were healed by heating films at 100 °C. [36] The heating treatment may damage organic carrier transport layers or accelerate ion diffusion of metal electrodes; moreover, perovskite devices usually operate at the room temperature. Thus, it is necessary to design a perovskite material with self-healing capability which does not need any harsh external stimuli.Herein, we design a moisture-triggered self-healing flexible perovskite photodetector with poly(vinyl alcohol) (PVA) as an additive.…”