Ultra-thin perovskite solar cells with high specific power density based on colorless polyimide substrates

Ultra-thin perovskite solar cells (UTPSCs) have garnered significant attention for their high specific power and potential application in space missions. However, the efficiency of ultra-thin solar cells has been constrained by challenges in handling and fabricating them on the fragile ultra-thin substrates, leading to notable performance disparities compared to their rigid counterparts. Here, we present a novel method for fabricating efficient and stable ultra-thin flexible PSCs. By employing a polydimethylsiloxane (PDMS) buffer layer and controlling the imidization temperature of colorless polyimide (CPI), we prepared an ultra-thin CPI substrate with a thickness of 1–3 μm, which can be easily peeled off. This technique provides a heat-resistant ultra-thin substrate with a smooth surface for UTPSC fabrication. Additionally, the ultra-thin substrate exhibits superior thermal conductivity and more uniform temperature distribution compared to conventional flexible substrates. Ultimately, we achieve a 1.5 μm UTPSC with a power conversion efficiency of 22.13 % and an outstanding specific power density of 50 W/g, surpassing most existing solar cells. Remarkably, the UTPSCs demonstrate exceptional mechanical robustness, maintaining performance even under rigorous bending and twisting. Moreover, CPI exhibited better thermal expansion matching with perovskite and demonstrated enhanced stability under low-temperature conditions and thermal cycling, showing potential for space applications. Our approach of preparing ultra-thin CPI substrates offers an effective pathway for fabricating lightweight and highly flexible electronics.