Synthesizing near‐ultraviolet absorbed donor for transparent polymer solar cells

Wavelength-selective transparent polymer solar cells (T-PSCs) have huge developing potential in power-window applications for their excellent visible transparency and high color-rendering index. However, the main research interest of devices until now is focused on near-infrared absorbers for both polymer donor and nonfullerene small-molecule acceptor (NF-SMA) due to the lack of appropriate near-ultraviolet absorbers. Herein, the successful implementation of the T-PSC devices based on novel kinds of near-ultraviolet polymer donors combined with a near-infrared NF-SMA Y6 is reported. The reported polymer donors are "D1-D2"-type copolymers employing fluorene and triphenylamine as the two electron-donating units. The best-performed one not only shows ultrawide optical bandgap (2.87 eV), leading to high average visible transmittance (AVT) of 96.8% in the thin film, but also has efficient hole mobility (about 5.0 10(-6) cm(2 )V(-1) s(-1)), well-matched frontier molecular orbital energy levels, and good miscibility with Y6. As a result, the T-PSC device is obtained with an AVT of 51.4% and PCE of 3.15%, along with favorable light utilization efficiency (LUE) of 1.62% and CRI of 91.6. This is the first example that uses near-ultraviolet-absorbed polymer donor to achieve high-efficiency T-PSC devices.