Bidirectional Voltage Regulation for Integrated Photovoltachromic Device Based on P3HT-Electrochromic Unit and Perovskite/Organic Tandem Solar Cells.

ABSTRACT

Integrated electrochromic devices powered by photovoltaic cells have evoked a lot of interest due to their promising commercial prospects. However, their application has been restricted by the voltage adaption between the self-powered voltage and the color-changing threshold voltage (Vt). Herein, a strategy of bidirectional voltage regulating is proposed to develop a novel stand-alone integrated photovoltachromic device (I-PVCD), which integrates perovskite/organic tandem solar cells (P/O-TSCs) to drive color-changing process of conjugated poly(3-hexylthiophene) (P3HT) films. To lower the driving-voltage of electrochromic layer, C60 is introduced to decrease the onset oxidation potential of P3HT film, and thus leading to a reduced Vt of 0.70 V benefiting from the enhanced highest occupied molecular orbital level and decreased charge transfer resistance from 67.46 to 49.89 Ω. Simultaneously, PBDB-T is utilized as the hole transport layer in the interconnecting layer of CsPbI2Br/PTB7-ThIEICO-4F P/O-TSC to improve its open-circuit voltage (Voc) to 1.85 V. Under their synergetic merits, a I-PVCD with a wider self-adaptive voltage range is achieved. This device can undergo fast and reversible chromic transition from beautiful magenta to transparent only under the solar radiation, and demonstrates a coloration efficiency of 351.90 cm2 C-1 and a switching time of 2 s besides its excellent operating reliability.